Selina Solutions Concise Mathematics Class 6 Chapter 19 Fundamental Operations has accurate answers, designed by subject matter experts at BYJU’S, in accordance with the grasping abilities of students. The solutions play a key role in improving students’ problem solving abilities in a short duration. Those who aim to achieve high marks in the annual examination are suggested to solve the textbook questions using these solutions. In order to obtain more conceptual knowledge, students can download Selina Solutions Concise Mathematics Class 6 Chapter 19 Fundamental Operations PDF, from the below mentioned links.
Chapter 19 provides in-depth knowledge relying on Fundamental Operations such as addition, subtraction, multiplication and division. Students who practice these solutions on a regular basis, learn multiple ways of solving complex problems effortlessly.
Selina Solutions Concise Mathematics Class 6 Chapter 19: Fundamental Operations Download PDF
Exercises of Selina Solutions Concise Mathematics Class 6 Chapter 19: Fundamental Operations
Access Selina Solutions Concise Mathematics Class 6 Chapter 19: Fundamental Operations
Exercise 19(A)
1. Fill in the blanks:
(i) 5 + 4 = …….. and 5x + 4x = ………
(ii) 12 + 18 = ……. and 12x2y + 18x2y = ……..
(iii) 7 + 16 = …….. and 7a + 16b = …….
(iv) 1 + 3 = ……. and x2y + 3xy2 = ……
(v) 7 – 4 = …… and 7ab – 4ab = ………
Solution:
(i) 5 + 4 = 9 and 5x + 4x = 9x
(ii) 12 + 18 = 30 and 12x2y + 18x2y = 30x2y
(iii) 7 + 16 = 23 and 7a + 16b = 7a + 16b
(iv) 1 + 3 = 4 and x2y + 3xy2 = x2y + 3xy2
(v) 7 – 4 = 3 and 7ab – 4ab = 3ab
2. Fill in the blanks:
(i) The sum of -2 and -5 = ……… and the sum of -2x and -5x = ……….
(ii) The sum of 8 and -3 = ……… and the sum of 8ab and -3ab = ………….
(iii) The sum of -15 and -4 = ……… and the sum of -15x and -4y = ………..
(iv) 15 + 8 + 3 = …….. and 15x + 8y + 3x = …………
(v) 12 – 9 + 15 = ………… and 12ab – 9ab + 15ba = ……….
Solution:
(i) The sum of -2 and -5 = – 7 and the sum of -2x and -5x = – 7x
(ii) The sum of 8 and -3 = 5 and the sum of 8ab and -3ab = 5ab
(iii) The sum of -15 and -4 = – 19 and the sum of -15x and -4y = – 15x – 4y
(iv) 15 + 8 + 3 = 26 and 15x + 8y + 3x = 18x + 8y
(v) 12 – 9 + 15 = 18 and 12ab – 9ab + 15ba = 18ab
3. Add:
(i) 8xy and 3xy
(ii) 2xyz, xyz and 6xyz
(iii) 2a, 3a and 4b
(iv) 3x and 2y
(v) 5m, 3n and 4p
Solution:
(i) 8xy and 3xy
The addition of 8xy and 3xy is calculated as follows
8xy + 3xy = 11xy
(ii) 2xyz, xyz and 6xyz
The addition of 2xyz, xyz and 6xyz is calculated as follows
2xyz + xyz + 6xyz = 9xyz
(iii) 2a, 3a and 4b
The addition of 2a, 3a and 4b is calculated as follows
2a + 3a + 4b = 5a + 4b
(iv) 3x and 2y
The addition of 3x and 2y is calculated as follows
3x + 2y = 3x + 2y
(v) 5m, 3n and 4p
The addition of 5m, 3n and 4p is calculated as follows
5m + 3n + 4p = 5m + 3n + 4p
4. Evaluate:
(i) 6a – a – 5a – 2a
(ii) 2b – 3b – b + 4b
(iii) 3x – 2x – 4x + 7x
(iv) 5ab + 2ab – 6ab + ab
(v) 8x – 5y – 3x + 10y
Solution:
(i) 6a – a – 5a – 2a
The value of given expression is calculated as below
6a – a – 5a – 2a = (6 – 1 – 5 – 2) a
We get,
= (5 – 5 – 2) a
= – 2a
Therefore, 6a – a – 5a – 2a = – 2a
(ii) 2b – 3b – b + 4b
The value of given expression is calculated as below
2b – 3b – b + 4b = 2b + 4b – (3 + 1) b
We get,
= 6b – 4b
= 2b
Therefore, 2b – 3b – b + 4b = 2b
(iii) 3x – 2x – 4x + 7x
The given expression is calculated as below
3x – 2x – 4x + 7x = 3x + 7x – 2x – 4x
= (3 + 7) x – (2 + 4) x
= 10x – 6x
= 4x
Therefore, 3x – 2x – 4x + 7x = 4x
(iv) 5ab + 2ab – 6ab + ab
The given expression is calculated as below
5ab + 2ab – 6ab + ab = 5ab + 2ab + ab – 6ab
We get,
= 8ab – 6ab
= 2ab
Therefore, 5ab + 2ab – 6ab + ab = 2ab
(v) 8x – 5y – 3x + 10y
The given expression is calculated as below
8x – 5y – 3x + 10y = 8x – 3x + 10y – 5y
= 5x + 5y
Therefore, 8x – 5y – 3x + 10y = 5x + 5y
5. Evaluate:
(i) -7x + 9x + 2x – 2x
(ii) 5ab – 2ab – 8ab + 6ab
(iii) -8a – 3a + 12a + 13a – 6a
(iv) 19abc – 11abc – 12abc + 14abc
Solution:
(i) -7x + 9x + 2x – 2x
The value of given expression is calculated as follows
-7x + 9x + 2x – 2x = 9x + 2x – 7x – 2x
= 11x – 9x
We get,
= 2x
Hence, -7x + 9x + 2x – 2x = 2x
(ii) 5ab – 2ab – 8ab + 6ab
The value of given expression is calculated as follows
5ab – 2ab – 8ab + 6ab = 5ab + 6ab – 2ab – 8ab
We get,
= 11ab – 10ab
= ab
Hence, 5ab – 2ab – 8ab + 6ab = ab
(iii) –8a – 3a + 12a + 13a – 6a
The value of given expression is calculated as follows
-8a – 3a + 12a + 13a – 6a = 12a + 13a – (8a + 3a + 6a)
= 25a – 17a
= 8a
Hence, -8a – 3a + 12a + 13a – 6a = 8a
(iv) 19abc – 11abc – 12abc + 14abc
The value of given expression is calculated as follows
19abc – 11abc – 12abc + 14abc = abc (19 – 11 – 12 + 14)
= abc (33 – 23)
= 10abc
Hence, 19abc – 11abc – 12abc + 14abc = 10abc
6. Subtract the first term from the second:
(i) 4ab, 6ba
(ii) 4.8b, 6.8b
(iii) 3.5abc, 10.5abc
(iv) 3(1 / 2) mn, 8(1 / 2)nm
Solution:
(i) 4ab, 6ba
The subtraction of first term from the second term is calculated as below
6ba – 4ab = 2ab
(ii) 4.8b, 6.8b
The subtraction of first term from the second term is calculated as below
6.8b – 4.8b = 2b
(iii) 3.5abc, 10.5abc
The subtraction of first term from the second term is calculated as below
10.5abc – 3.5abc = 7abc
(iv) 3(1 / 2) mn, 8(1 / 2)nm
The subtraction of first term from the second term is calculated as below
8(1 / 2)nm – 3 (1 / 2) mn = (17 / 2)nm – (7 / 2)mn
We get,
= [(17mn – 7mn) / 2]
= (10 / 2)mn
= 5mn
7. Simplify:
(i) 2a2b2 + 5ab2 + 8a2b2 – 3ab2
(ii) 4a + 3b – 2a – b
(iii) 2xy + 4yz + 5xy + 3yz – 6xy
(iv) ab + 15ab – 11ab – 2ab
(v) 6a2 – 3b2 + 2a2 + 5b2 – 4a2
Solution:
(i) 2a2b2 + 5ab2 + 8a2b2 – 3ab2
The simplified form of the given expression is calculated as follows
2a2b2 + 5ab2 + 8a2b2 – 3ab2 = 2a2b2 + 8a2b2 + 5ab2 – 3ab2
We get,
= 10a2b2 + 2ab2
Therefore, 2a2b2 + 5ab2 + 8a2b2 – 3ab2 = 10a2b2 + 2ab2
(ii) 4a + 3b – 2a – b
The simplified form of the given expression is calculated as follows
4a + 3b – 2a – b = 4a – 2a + 3b – b
= 2a + 2b
Therefore, 4a + 3b – 2a – b = 2a + 2b
(iii) 2xy + 4yz + 5xy + 3yz – 6xy
The simplified form of the given expression is calculated as follows
2xy + 4yz + 5xy + 3yz – 6xy = 2xy + 5xy – 6xy + 4yz + 3yz
= xy + 7yz
Therefore, 2xy + 4yz + 5xy + 3yz – 6xy = xy + 7yz
(iv) ab + 15ab – 11ab – 2ab
The simplified form of the given expression is calculated as follows
ab + 15ab – 11ab – 2ab = 16ab – 13ab
= 3ab
Therefore, ab + 15ab – 11ab – 2ab = 3ab
(v) 6a2 – 3b2 + 2a2 + 5b2 – 4a2
The simplified form of the given expression is calculated as follows
6a2 – 3b2 + 2a2 + 5b2 – 4a2 = 6a2 + 2a2 – 4a2 + 5b2 – 3b2
We get,
= 4a2 + 2b2
Therefore, 6a2 – 3b2 + 2a2 + 5b2 – 4a2 = 4a2 + 2b2
Exercise 19(B)
1. Find the sum of:
(i) 3a + 4b + 7c, – 5a + 3b – 6c
and 4a – 2b – 4c
(ii) 2x2 + xy – y2, – x2 + 2xy + 3y2
and 3x2 – 10xy + 4y2
(iii) x2 – x + 1, -5x2 + 2x – 2
and 3x2 – 3x + 1
(iv) a2 – ab + bc, 2ab + bc – 2a2
and – 3bc + 3a2 + ab
(v) 4x2 + 7 – 3x, 4x – x2 + 8
and – 10 + 5x – 2x2
Solution:
(i) 3a + 4b + 7c, – 5a + 3b – 6c
and 4a – 2b – 4c
The sum of 3a + 4b + 7c, – 5a + 3b – 6c and 4a – 2b – 4c is calculated as shown below
(3a + 4b + 7c) + (-5a + 3b – 6c) + (4a – 2b – 4c)
= 3a + 4a – 5a + 4b + 3b – 2b + 7c – 6c – 4c
We get,
= 2a +5b – 3c
Hence, the sum of 3a + 4b + 7c, – 5a + 3b – 6c and 4a – 2b – 4c is 3c
(ii) 2x2 + xy – y2, – x2 + 2xy + 3y2
and 3x2 – 10xy + 4y2
The sum of 2x2 + xy – y2, – x2 + 2xy + 3y2 and 3x2 – 10xy + 4y2 is calculated as shown below
(2x2 + xy – y2) + (- x2 + 2xy + 3y2) + (3x2 – 10xy + 4y2)
= 2x2 – x2 + 3x2 + xy + 2xy – 10xy + 3y2 + 4y2 – y2
We get,
= 4x2 – 7xy + 6y2
Hence, the sum of 2x2 + xy – y2, – x2 + 2xy + 3y2 and 3x2 – 10xy + 4y2 is 4x2 – 7xy + 6y2
(iii) x2 – x + 1, -5x2 + 2x – 2 and 3x2 – 3x + 1
The sum of (x2 – x + 1), (- 5x2 + 2x – 2) and (3x2 – 3x + 1) is calculated as shown below
(x2 – x + 1) + (- 5x2 + 2x – 2) + (3x2 – 3x + 1)
= x2 – 5x2 + 3x2 + 2x – x – 3x + 1 +1 – 2
= – x2 – 2x
Hence, the sum of (x2 – x + 1), (- 5x2 + 2x – 2) and (3x2 – 3x + 1) is – x2 – 2x
(iv) a2 – ab + bc, 2ab + bc – 2a2 and – 3bc + 3a2 + ab
The sum of (a2 – ab + bc), (2ab + bc – 2a2) and (- 3bc + 3a2 + ab) is calculated as shown below
(a2 – ab + bc) + (2ab + bc – 2a2) + (- 3bc + 3a2 + ab)
= a2 – 2a2 + 3a2 + 2ab + ab – ab + bc + bc – 3bc
We get,
= 2a2 +2ab – bc
Hence, the sum of (a2 – ab + bc), (2ab + bc – 2a2) and (- 3bc + 3a2 + ab) is 2a2 +2ab – bc
(v) 4x2 + 7 – 3x, 4x – x2 + 8 and – 10 + 5x – 2x2
The sum of (4x2 + 7 – 3x), (4x – x2 + 8) and (- 10 + 5x – 2x2) is calculated as shown below
(4x2 + 7 – 3x) + (4x – x2 + 8) + (- 10 + 5x – 2x2)
= 4x2 – x2 – 2x2 + 7 + 8 – 10 + 4x + 5x – 3x
We get,
= x2 + 5 + 6x
Hence, the sum of (4x2 + 7 – 3x), (4x – x2 + 8) and (- 10 + 5x – 2x2) is x2 + 5 + 6x
2.Add the following expressions:
(i) – 17x2 – 2xy + 23y2, – 9y2 + 15x2 + 7xy
and 13x2 + 3y2 – 4xy
(ii) – x2 – 3xy + 3y2 + 8, 3x2 – 5y2 – 3 + 4xy
and – 6xy + 2x2 – 2 + y2
(iii) a3 – 2b3 + a, b3 – 2a3 + b
and – 2b + 2b3 – 5a + 4a3
Solution:
(i) The sum of (– 17x2 – 2xy + 23y2), (- 9y2 + 15x2 + 7xy) and (13x2 + 3y2 – 4xy) is calculated as follows
(– 17x2 – 2xy + 23y2) + (- 9y2 + 15x2 + 7xy) + (13x2 + 3y2 – 4xy)
= – 17x2 + 15x2 + 13x2 – 2xy – 4xy + 7xy + 23y2 + 3y2 – 9y2
We get,
= 11x2 + xy + 17y2
Therefore, the sum of (– 17x2 – 2xy + 23y2), (- 9y2 + 15x2 + 7xy) and (13x2 + 3y2 – 4xy) is 11x2 + xy + 17y2
(ii) – x2 – 3xy + 3y2 + 8, 3x2 – 5y2 – 3 + 4xy and – 6xy + 2x2 – 2 + y2
The sum of (– x2 – 3xy + 3y2 + 8), (3x2 – 5y2 – 3 + 4xy) and (– 6xy + 2x2 – 2 + y2) is calculated as follows
(– x2 – 3xy + 3y2 + 8) + (3x2 – 5y2 – 3 + 4xy) + (– 6xy + 2x2 – 2 + y2)
= – x2 + 3x2 + 2x2 – 3xy – 6xy + 4xy + 3y2 + y2 – 5y2 + 8 – 3 – 2
We get,
= 4x2 – 5xy – y2 + 3
Therefore, the sum of (– x2 – 3xy + 3y2 + 8), (3x2 – 5y2 – 3 + 4xy) and (– 6xy + 2x2 – 2 + y2) is 4x2 – 5xy – y2 + 3
(iii) a3 – 2b3 + a, b3 – 2a3 + b and – 2b + 2b3 – 5a + 4a3
The sum of (a3 – 2b3 + a), (b3 – 2a3 + b) and (– 2b + 2b3 – 5a + 4a3) is calculated as follows
(a3 – 2b3 + a) + (b3 – 2a3 + b) + (– 2b + 2b3 – 5a + 4a3)
= a3 + 4a3 – 2a3 – 2b3 + b3 + 2b3 + a – 5a + b – 2b
We get,
= 3a3 + b3 – 4a – b
Therefore, the sum of (a3 – 2b3 + a), (b3 – 2a3 + b) and (– 2b + 2b3 – 5a + 4a3) is 3a3 + b3 – 4a – b
3. Evaluate:
(i) 3a – (a + 2b)
(ii) (5x – 3y) – (x + y)
(iii) (8a + 15b) – (3b – 7a)
(iv) (8x + 7y) – (4y – 3x)
(v) 7 – (4a – 5)
Solution:
(i) 3a – (a + 2b)
The value of the given expression is calculated as below
3a – (a + 2b)
= 3a – a – 2b
= 2a – 2b
Taking 2 as common, we get
= 2(a – b)
(ii) (5x – 3y) – (x + y)
The value of the given expression is calculated as below
(5x – 3y) – (x + y)
= 5x – x – 3y – y
= 4x – 4y
Taking 4 as common, we get
= 4(x – y)
(iii) (8a + 15b) – (3b – 7a)
The value of the given expression is calculated as below
(8a + 15b) – (3b – 7a)
= 8a + 7a + 15b – 3b
On calculation, we get
= 15a + 12b
(iv) (8x + 7y) – (4y – 3x)
The value of the given expression is calculated as below
(8x + 7y) – (4y – 3x)
= 8x + 3x + 7y – 4y
On further calculation, we get
= 11x + 3y
(v) 7 – (4a – 5)
The value of the given expression is calculated as below
7 – (4a – 5)
= 7 – 4a + 5
We get,
= 12 – 4a
4. Subtract:
(i) 5a – 3b + 2c from a – 4b – 2c
(ii) 4x – 6y + 3z from 12x + 7y – 21z
(iii) 5 – a – 4b + 4c from 5a – 7b + 2c
(iv) – 8x – 12y + 17z from x – y – z
(v) 2ab + cd – ac – 2bd from ab – 2cd + 2ac + bd
Solution:
(i) 5a – 3b + 2c from a – 4b – 2c
The value of the subtraction is calculated as follows
(a – 4b – 2c) – (5a – 3b + 2c)
= a – 5a – 4b + 3b – 2c – 2c
We get,
= – 4a – b – 4c
(ii) 4x – 6y + 3z from 12x + 7y – 21z
The value of the subtraction is calculated as follows
(12x + 7y – 21z) – (4x – 6y + 3z)
= 12x – 4x + 7y + 6y – 21z – 3z
On further calculation, we get
= 8x + 13y – 24z
(iii) 5 – a – 4b + 4c from 5a – 7b + 2c
The value of the subtraction is calculated as follows
(5a – 7b + 2c) – (5 – a – 4b + 4c)
= 5a + a – 7b + 4b + 2c – 4c – 5
We get,
=6a – 3b – 2c – 5
(iv) – 8x – 12y + 17z from x – y – z
The value of the subtraction is calculated as follows
(x – y – z) – (- 8x – 12y + 17z)
= x + 8x + 12y – y – z – 17z
We get,
= 9x + 11y – 18z
(v) 2ab + cd – ac – 2bd from ab – 2cd + 2ac + bd
The value of the subtraction is calculated as follows
(ab – 2cd + 2ac + bd) – (2ab + cd – ac – 2bd)
= ab – 2ab – 2cd – cd + 2ac + ac + bd + 2bd
On calculating further, we get
= – ab – 3cd + 3ac + 3bd
5.
(i) Take – ab + bc – ca from bc – ca + ab.
(ii) Take 5x + 6y – 3z from 3x + 5y – 4z.
(iii) Take (-3 / 2) p + q – r from (1 / 2)p – (1 / 3)q – (3 / 2) r
(iv) Take 1 – a + a2 from a2 + a + 1
Solution:
(i) The value of the subtraction is calculated as,
(bc – ca + ab) – (-ab + bc – ca)
= bc – bc – ca + ca + ab + ab
We get,
= 2ab
Hence, (bc – ca + ab) – (-ab + bc – ca) = 2ab
(ii) The value of the subtraction is calculated as,
(3x + 5y – 4z) – (5x + 6y – 3z)
= 3x – 5x + 5y – 6y – 4z + 3z
On simplification, we get
= – 2x – y – z
Hence, (3x + 5y – 4z) – (5x + 6y – 3z) = – 2x – y – z
(iii) The value of the subtraction is calculated as,
[(1 / 2)p – (1 / 3)q – (3 / 2) r] – [(-3 / 2) p + q – r]= (1 / 2)p + (3 / 2)p – (1 / 3)q – q – (3 / 2)r + r
On further calculation, we get
= 2p – (4 / 3)q – (1 / 2)r
Hence, [(1 / 2)p – (1 / 3)q – (3 / 2) r] – [(-3 / 2) p + q – r] = 2p – (4 / 3)q – (1 / 2)r
(iv) The value of the subtraction is calculated as,
(a2 + a + 1) – (1 – a + a2)
= a2 – a2 + a + a + 1 – 1
We get,
= a + a
= 2a
6. From the sum of x + y – 2z and 2x – y + z subtract x + y + z.
Solution:
The value of terms as per the question is calculated as follows
(x + y – 2z) + (2x – y + z) – (x + y + z)
= x + 2x – x + y – y – y – 2z – z + z
We get,
= 2x – y – 2z
Therefore, (x + y – 2z) + (2x – y + z) – (x + y + z) = 2x – y – 2z
7. From the sum of 3a – 2b + 4c and 3b – 2c subtract a – b – c.
Solution:
The value of terms as per the question is calculated as shown below
(3a – 2b + 4c) + (3b – 2c) – (a – b – c)
= 3a – 2b + 4c + 3b – 2c – a + b + c
On further calculation, we get
= 3a – a + 3b + b – 2b + 4c + c – 2c
= 2a + 2b + 3c
Hence, (3a – 2b + 4c) + (3b – 2c) – (a – b – c) = 2a + 2b + 3c
8. Subtract x – 2y – z from the sum of 3x – y + z and x + y – 3z.
Solution:
The value of terms as per the question is calculated as follows
(3x – y + z) + (x + y – 3z) – (x – 2y – z)
= 3x + x – x – y + y + 2y + z – 3z + z
We get,
= 3x + 2y – z
Therefore, (3x – y + z) + (x + y – 3z) – (x – 2y – z) = 3x + 2y – z
9. Subtract the sum of x + y and x – z from the sum of x – 2z and x + y + z
Solution:
The value of terms as per the question is calculated as follows
(x – 2z) + (x + y + z) – {(x + y) + (x – z)}
On further calculation, we get
= x + x – x –x + y – y + z + z – 2z
We get,
= 0
Therefore, (x – 2z) + (x + y + z) – {(x + y) + (x – z)} = 0
10. By how much should x + 2y – 3z be increased to get 3x?
Solution:
The terms calculated as per the question is as follows
3x – (x + 2y – 3z)
= 3x – x – 2y + 3z
We get,
= 2x – 2y + 3z
11. The sum of two expressions is 5x2 – 3y2. If one of them is 3x2 + 4xy – y2, find the other.
Solution:
The other expression is calculated as follows
(5x2 – 3y2) – (3x2 + 4xy – y2)
= 5x2 – 3x2 – 4xy – 3y2 + y2
We get,
= 2x2 – 4xy – 2y2
12. The sum of two expressions is 3a2 + 2ab – b2. If one of them is 2a2 + 3b2, find the other.
Solution:
The other expression is calculated as follows
(3a2 + 2ab – b2) – (2a2 + 3b2)
On simplification, we get
=3a2 – 2a2 – b2 – 3b2 + 2ab
= a2– 4b2 + 2ab
Exercise 19(C)
1. Fill in the blanks:
(i) 6 × 3 = ………. and 6x × 3x = …………
(ii) 6 × 3 = ……… and 6x2 × 3x3 = …………
(iii) 5 × 4 = ………. and 5x × 4y = …………
(iv) 4 × 7 = …………. and 4ax × 7x = ……….
(v) 6 × 2 = …………. and 6xy × 2xy = ……….
Solution:
(i) 6 × 3 = 18
Hence,
6x × 3x = 6 × 3 × x × x
We get,
= 18 × x2
= 18x2
Therefore, 6 × 3 = 18 and 6x × 3x = 18x2
(ii) 6 × 3 = 18
Hence,
6x2 × 3x3 = 6 × 3 × x2 + 3
= 18 × x5
= 18x5
Therefore, 6 × 3 = 18 and 6x2 × 3x3 = 18x5
(iii) 5 × 4 = 20 and 5x × 4y = 5 × 4 × x × y
= 20xy
Therefore, 5 × 4 = 20 and 5x × 4y = 20xy
(iv) 4 × 7 = 28
Hence,
4ax × 7x = 4 × 7 × a × x × x
= 28 × a × x2
= 28ax2
Therefore, 4 × 7 = 28 and 4ax × 7x = 28ax2
(v) 6 × 2 = 12
Hence,
6xy × 2xy = 6 × 2 × x1 + 1 × y1 + 1
= 12 × x2 × y2
= 12x2y2
Therefore, 6 × 2 = 12 and 6xy × 2xy = 12x2y2
2. Fill in the blanks:
(i) 4x × 6x × 2 = ………
(ii) 3ab × 6ax = …………
(iii) x × 2x2 × 3x3 = ………
(iv) 5 × 5a3 = …………
(v) 6 × 6x2 × 6x2y2 = ………
Solution:
(i) 4x × 6x × 2 = 4 × 6 × 2 × x × x
= 48 × x2
We get,
= 48x2
Hence, 4x × 6x × 2 = 48x2
(ii) 3ab × 6ax = 3 × 6 × a × a × b × x
= 18 × a2 × b × x
We get,
= 18a2bx
Hence, 3ab × 6ax = 18a2bx
(iii) x × 2x2 × 3x3 = 2 × 3 × x × x2 × x3
= 6 × x1 + 2 + 3
= 6 × x6
= 6x6
Hence, x × 2x2 × 3x3 = 6x6
(iv) 5 × 5a3 = 5 × 5 × a3
= 25 × a3
We get,
= 25a3
Hence, 5 × 5a3 = 25a3
(v) 6 × 6x2 × 6x2y2 = 6 × 6 × 6 × x2 × x2 × y2
= 216 × x2+ 2 × y2
= 216 × x4 × y2
We get,
= 216x4y2
Hence, 6 × 6x2 × 6x2y2 = 216x4y2
3. Find the value of:
(i) 3x3 × 5x4
(ii) 5a2 × 7a7
(iii) 3abc × 6ac3
(iv) a2b2 × 5a3b4
(v) 2x2y3 × 5x3y4
Solution:
(i) 3x3 × 5x4
3x3 × 5x4 = 3 × 5 × x3 × x4
= 15 × x3 + 4
We get,
= 15 × x7
= 15x7
Hence, the value of 3x3 × 5x4 is 15x7
(ii) 5a2 × 7a7
5a2 × 7a7 = 5 × 7 × a2 × a7
= 35 × a2 + 7
= 35 × a9
We get,
= 35a9
Hence, the value of 5a2 × 7a7 is 35a9
(iii) 3abc × 6ac3
3abc × 6ac3 = 3 × 6 × a × a × b × c × c3
=18 × a1+ 1 × b × c1+3
= 18 × a2 × b × c4
We get,
= 18a2bc4
Hence, the value of 3abc × 6ac3 is 18a2bc4
(iv) a2b2 × 5a3b4
a2b2 × 5a3b4 = 5 × a2 × a3 × b2 × b4
= 5 × a2+3 × b2+4
= 5 × a5 × b6
We get,
= 5a5b6
Hence, the value of a2b2 × 5a3b4 is 5a5b6
(v) 2x2y3 × 5x3y4
2x2y3 × 5x3y4 = 2 × 5 × x2 × x3 × y3 × y4
= 10 × x2+3 × y3+4
We get,
= 10 × x5 × y7
= 10x5y7
Hence, the value of 2x2y3 × 5x3y4 is 10x5y7
4. Multiply:
(i) a + b by ab
(ii) 3ab – 4b by 3ab
(iii) 2xy – 5by by 4bx
(iv) 4x + 2y by 3xy
(v) 1 + 4x by x
Solution:
(i) a + b by ab
The multiplication of a + b by ab is calculated as,
(a + b) × ab = a × ab + b × ab
= a1+1b + ab1+1
We get,
= a2b + ab2
Hence, (a + b) by ab = a2b + ab2
(ii) 3ab – 4b by 3ab
The multiplication of 3ab – 4b by 3ab is calculated as,
(3ab – 4b) × 3ab = 3ab × 3ab – 4b × 3ab
= 9a1+1b1+1 – 12ab1+1
We get,
= 9a2b2 – 12ab2
Therefore, (3ab – 4b) by 3ab = 9a2b2 – 12ab2
(iii) 2xy – 5by by 4bx
The multiplication of 2xy – 5by by 4bx is calculated as,
(2xy – 5by) × 4bx = 2xy × 4bx – 5by × 4bx
= 8bx1+1y – 20b1+1xy
We get,
= 8bx2y – 20b2xy
Therefore, (2xy – 5by) by 4bx = 8bx2y – 20b2xy
(iv) 4x + 2y by 3xy
The multiplication of 4x + 2y by 3xy is calculated as,
(4x + 2y) × 3xy = 4x × 3xy + 2y × 3xy
On simplification, we get
= 12x1+1y + 6xy1+1
= 12x2y + 6xy2
Therefore, (4x + 2y) by 3xy = 12x2y + 6xy2
(v) 1 + 4x by x
The multiplication of (1 + 4x) by x is calculated as,
(1 + 4x) × x = 1 × x + 4x × x
On simplification, we get
= x + 4x1+1
= x + 4x2
Therefore, (1 + 4x) by x = x + 4x2
5. Multiply:
(i) – x + y – z and – 2x
(ii) xy – yz and x2yz2
(iii) 2xyz + 3xy and – 2y2z
(iv) – 3xy2 + 4x2y and – xy
(v) 4xy and – x2y – 3x2 y2
Solution:
(i) – x + y – z and – 2x
The multiplication of the given expression is calculated as,
(- x + y – z) × – 2x = – x × – 2x + y × – 2x – z × – 2x
On further calculation, we get
= 2x1+1 – 2xy + 2xz
= 2x2 – 2xy + 2xz
Hence, the multiplication of (- x + y – z) and – 2x is 2x2 – 2xy + 2xz
(ii) xy – yz and x2yz2
The multiplication of the given expression is calculated as,
(xy – yz) × (x2yz2) = xy × x2yz2 – yz × x2yz2
We get,
= x1+2y1+1z2 – x2y1+1z1+2
= x3y2z2 – x2y2z3
Hence, the multiplication of (xy – yz) and x2yz2 = x3y2z2 – x2y2z3
(iii) 2xyz + 3xy and – 2y2z
The multiplication of the given expression is calculated as,
(2xyz + 3xy) × – 2y2z = 2xyz × – 2y2z + 3xy × – 2y2z
On further calculation, we get
= – 4xy1+2z1+1 – 6xy1+2z
= – 4xy3z2 – 6xy3z
Hence, the multiplication of 2xyz + 3xy and – 2y2z = – 4xy3z2 – 6xy3z
(iv) – 3xy2 + 4x2y and – xy
The multiplication of the given expression is calculated as,
(- 3xy2 + 4x2y) × – xy = 3x1+1y2+1 – 4x2+1y1+1
On calculation, we get
= 3x2y3 – 4x3y2
Hence, the multiplication of – 3xy2 + 4x2y and – xy = 3x2y3 – 4x3y2
(v) 4xy and – x2y – 3x2 y2
The multiplication of the given expression is calculated as,
(- x2y – 3x2y2) × 4xy = – x2y × 4xy – 3x2y2 × 4xy
On further calculation, we get
= – 4x2+1y1+1 – 12x2+1y2+1
= – 4x3y2 – 12x3y3
Hence, the multiplication of 4xy and – x2y – 3x2 y2 = – 4x3y2 – 12x3y3
6. Multiply:
(i) 3a + 4b – 5c and 3a
(ii) – 5xy and – xy2 – 6x2y
Solution:
(i) 3a + 4b – 5c and 3a
The multiplication of the given expression is calculated as,
(3a + 4b – 5c) × 3a = 3a × 3a + 4b × 3a – 5c × 3a
On further calculation, we get
= 9a1+1 + 12ab – 15ac
= 9a2 + 12ab – 15ac
Therefore, the multiplication of 3a + 4b – 5c and 3a = 9a2 + 12ab – 15ac
(ii) – 5xy and – xy2 – 6x2y
The multiplication of the given expression is calculated as,
– 5xy × (- xy2 – 6x2y) = – 5xy × – xy2 – 5xy × – 6x2y
On further calculation, we get
= 5x1+1y1+2 + 30x1+2y1+1
= 5x2y3 + 30x3y2
Therefore, the multiplication of – 5xy and – xy2 – 6x2y = 5x2y3 + 30x3y2
7. Multiply:
(i) x + 2 and x + 10
(ii) x + 5 and x – 3
(iii) x – 5 and x + 3
(iv) x – 5 and x – 3
(v) 2x + y and x + 3y
Solution:
(i) x + 2 and x + 10
The given expression is calculated as follows
(x + 2) × (x + 10) = x × (x + 10) + 2 × (x + 10)
We get,
= x2 + 10x + 2x + 20
= x2 + 12x + 20
Hence, the multiplication of (x + 2) and (x + 10) = x2 + 12x + 20
(ii) x + 5 and x – 3
The given expression is calculated as follows
(x + 5) × (x – 3) = x × (x – 3) + 5 × (x – 3)
On simplification, we get
= x2 – 3x + 5x – 15
= x2 + 2x – 15
Hence, the multiplication of (x + 5) and (x – 3) = x2 + 2x – 15
(iii) x – 5 and x + 3
The given expression is calculated as follows
(x – 5) × (x + 3) = x × (x + 3) – 5 × (x + 3)
On further calculation, we get
= x2 + 3x – 5x – 15
= x2 – 2x – 15
Hence, the multiplication of (x – 5) and (x + 3) = x2 – 2x – 15
(iv) x – 5 and x – 3
The given expression is calculated as,
(x – 5) × (x – 3) = x × (x – 3) – 5 × (x – 3)
On further calculation, we get
= x2 – 3x – 5x + 15
= x2 – 8x + 15
Hence, the multiplication of (x – 5) and (x – 3) = x2 – 8x + 15
(v) 2x + y and x + 3y
The given expression is calculated as,
(2x + y) × (x + 3y) = 2x × (x + 3y) + y × (x + 3y)
On simplification, we get
= 2x2 + 6xy + xy + 3y2
= 2x2 + 7xy + 3y2
Hence, the multiplication of (2x + y) and (x + 3y) = 2x2 + 7xy + 3y2
8. Multiply:
(i) 3abc and – 5a2b2c
(ii) x – y + z and -2x
(iii) 2x – 3y – 5z and -2y
(iv) – 8xyz + 10 x2yz3 and xyz
(v) xyz and – 13xy2z + 15x2yz – 6xyz2
Solution:
(i) 3abc and – 5a2b2c
The given expression is calculated as follows,
3abc × – 5a2b2c = 3 × – 5 × a × a2 × b × b2 × c × c
On further calculation, we get
= – 15 × a1+2 × b1+2 × c1+1
= – 15 × a3 × b3 × c2
= – 15a3b3c2
Therefore, the multiplication of 3abc and – 5a2b2c = – 15a3b3c2
(ii) x – y + z and -2x
The given expression is calculated as follows,
(x – y + z) × – 2x = x × – 2x – y × – 2x + z × – 2x
On simplification, we get
= – 2x1+1 + 2xy – 2xz
= – 2x2 + 2xy – 2xz
Therefore, the multiplication of x – y + z and -2x = – 2x2 + 2xy – 2xz
(iii) 2x – 3y – 5z and -2y
The given expression is calculated as follows,
(2x – 3y – 5z) × – 2y = 2x × – 2y – 3y × – 2y – 5z × – 2y
On further calculation, we get
= – 4xy + 6y1+1 + 10yz
= – 4xy + 6y2 + 10yz
Therefore, the multiplication of 2x – 3y – 5z and -2y = – 4xy + 6y2 + 10yz
(iv) – 8xyz + 10 x2yz3 and xyz
The given expression is calculated as follows,
(- 8xyz + 10x2yz3) × xyz = – 8xyz × xyz + 10x2yz3 × xyz
On further calculation, we get
= – 8x1+1y1+1z1+1 + 10x2+1y1+1z3+1
= – 8x2y2z2 + 10x3y2z4
Therefore, the multiplication of – 8xyz + 10 x2yz3 and xyz = – 8x2y2z2 + 10x3y2z4
(v) xyz and – 13xy2z + 15x2yz – 6xyz2
The given expression is calculated as follows,
xyz × (- 13xy2z + 15x2yz – 6xyz2) = xyz × – 13xy2z + xyz ×15x2yz – xyz × 6xyz2
On simplification, we get
= – 13x1+1y1+2z1+1 + 15x1+2y1+1z1+1 – 6x1+1y1+1z1+2
We get,
= – 13x2y3z2 + 15x3y2z2 – 6x2y2z3
Therefore, the multiplication of xyz and – 13xy2z + 15x2yz – 6xyz2 = – 13x2y3z2 + 15x3y2z2 – 6x2y2z3
9. Find the product of:
(i) xy – ab and xy + ab
(ii) 2abc – 3xy and 2abc + 3xy
(iii) a + b – c and 2a – 3b
(iv) 5x – 6y – 7z and 2x + 3y
(v) 5x – 6y – 7z and 2x + 3y + z
Solution:
(i) xy – ab and xy + ab
The product of the given expression is calculated as,
(xy – ab) × (xy + ab) = xy × (xy + ab) – ab × (xy + ab)
On simplification, we get
= xy × xy + xy × ab – ab × xy – ab × ab
= x2y2 + abxy – abxy – a2b2
= x2y2 – a2b2
Hence, the product of (xy – ab) and (xy + ab) = x2y2 – a2b2
(ii) 2abc – 3xy and 2abc + 3xy
The product of the given expression is calculated as,
(2abc – 3xy) × (2abc + 3xy)
= 2abc × (2abc + 3xy) – 3xy × (2abc + 3xy)
We get,
= 2abc × 2abc + 2abc × 3xy – 3xy × 2abc – 3xy × 3xy
= 4a2b2c2 + 6abcxy – 6abcxy – 9x2y2
= 4a2b2c2 – 9x2y2
Hence, the product of 2abc – 3xy and 2abc + 3xy = 4a2b2c2 – 9x2y2
(iii) a + b – c and 2a – 3b
The product of the given expression is calculated as,
(a + b – c) × (2a – 3b)
= a × (2a – 3b) + b × (2a – 3b) – c × (2a – 3b)
= a × 2a – a × 3b + b × 2a – b × 3b – c × 2a + c × 3b
= 2a1+1 – 3ab + 2ab – 3b1+1 – 2ac + 3bc
We get,
= 2a2 – ab – 3b2 – 2ac + 3bc
Hence, the product of a + b – c and 2a – 3b = 2a2 – ab – 3b2 – 2ac + 3bc
(iv) 5x – 6y – 7z and 2x + 3y
The product of the given expression is calculated as,
(5x – 6y – 7z) × (2x + 3y)
= (5x – 6y – 7z) × 2x + (5x – 6y – 7z) × 3y
= 5x × 2x – 6y × 2x – 7z × 2x + 5x × 3y – 6y × 3y – 7z × 3y
We get,
= 10x2 – 12xy – 14xz + 15xy – 18y2 – 21yz
= 10x2 + 3xy – 14xz – 18y2 – 21yz
Hence, the product of 5x – 6y – 7z and 2x + 3y = 10x2 + 3xy – 14xz – 18y2 – 21yz
(v) 5x – 6y – 7z and 2x + 3y + z
The product of the given expression is calculated as,
(5x – 6y – 7z) × (2x + 3y + z)
= (5x – 6y – 7z) × 2x + (5x – 6y – 7z) × 3y + (5x – 6y – 7z) × z
= 5x × 2x – 6y × 2x – 7z × 2x + 5x × 3y – 6y × 3y – 7z × 3y + 5x × z – 6y × z – 7z × z
We get,
= 10x2 – 12xy – 14xz + 15xy – 18y2 – 21yz + 5xz – 6yz – 7z2
= 10x2 – 12xy + 15xy – 14xz + 5xz – 18y2 – 21yz – 6yz – 7z2
= 10x2 + 3xy – 9xz – 18y2 – 27yz – 7z2
Hence, the product of 5x – 6y – 7z and 2x + 3y + z = 10x2 + 3xy – 9xz – 18y2 – 27yz – 7z2
Exercise 19(D)
1. Divide:
(i) 3a by a
(ii) 15x by 3x
(iii) 16m by 4
(iv) 20x2 by 5x
(v) 30p2 by 10p2
Solution:
(i) 3a by a
3a ÷ a
This can be written as,
3a / a = (3 × a) / a
= 3
Hence, 3a ÷ a = 3
(ii) 15x by 3x
15x ÷ 3x
15x / 3x = (15 × x) / (3 × x)
This can be written as,
= (3 × 5 × x) / (3 × x)
We get,
= 5
Hence, 15x ÷ 3x = 5
(iii) 16m by 4
16m ÷ 4
16m / 4 = (16 × m) / 4
This can be written as,
= (4 × 4 × m) / 4
We get,
= 4m
Hence, 16m ÷ 4 = 4m
(iv) 20x2 by 5x
20x2 ÷ 5x
20x2 / 5x = (20 × x2) / (5 × x)
This can be written as,
= (4 × 5 × x2-1) / 5
= 4 × x
= 4x
Hence, 20x2 ÷ 5x = 4x
(v) 30p2 by 10p2
30p2 ÷ 10p2 = (30 × p2) / (10 × p2)
This can be written as,
= (3 × 10 × p2-2) / 10
= 3 × p0
= 3 × 1
= 3
Hence, 30p2 ÷ 10p2 = 3
2. Simplify:
(i) 2x5 ÷ x2
(ii) 6a8 ÷ 3a3
(iii) 20xy ÷ – 5xy
(iv) – 24a2b2c2 ÷ 6ab
(v) – 5x2y ÷ xy2
Solution:
(i) 2x5 ÷ x2
= (2 × x5) / x2
= 2 × x5-2
= 2 × x3
We get,
= 2x3
Hence, 2x5 ÷ x2 = 2x3
(ii) 6a8 ÷ 3a3
= (6 × a8) / (3 × a3)
This can be written as,
= (2 × 3 × a8-3) / 3
We get,
= 2 × a5
= 2a5
Hence, 6a8 ÷ 3a3 = 2a5
(iii) 20xy ÷ – 5xy
= (20 × x × y) / (- 5 × x × y)
This can be written as,
= (4 × 5) / – 5
We get,
= – 4
Hence, 20xy ÷ – 5xy = – 4
(iv) – 24a2b2c2 ÷ 6ab
= (- 24 × a2 × b2 × c2) / (6 × a × b)
This can be written as,
= (-4 × 6 × a2-1 × b2-1 × c2) / 6
We get,
= – 4 × a × b × c2
= – 4abc2
Hence, – 24a2b2c2 ÷ 6ab = – 4abc2
(v) – 5x2y ÷ xy2
= (- 5 × x2 × y) / (x × y2)
This can be written as,
= (- 5 × x2-1) / y2-1
We get,
= (- 5 × x) / y
= – 5x / y
Hence, – 5x2y ÷ xy2 = – 5x / y
3. Divide:
(i) (- 3m / 4) by 2m
(ii) – 15p6q8 by – 5p6q7
(iii) – 21m5n7 by 14m2n2
(iv) 36a4x5y6 by 4x2a3y2
(v) 20x3a6 by 5xy
Solution:
(i) (- 3m / 4) by 2m
= – 3m / 4 ÷ 2m = – 3m / 4 × 1 / 2m
= – (3 × m) / (4 × 2 × m)
We get,
= – 3 / 8
Hence, (- 3m / 4) ÷ 2m = – 3 / 8
(ii) – 15p6q8 by – 5p6q7
– 15p6q8 ÷ – 5p6q7 = (- 15 × p6 × q8) / (- 5 × p6 × q7)
This can be written as,
= (3 × 5 × q8-7) / 5
We get,
= 3 × q
= 3q
Hence, – 15p6q8 ÷ – 5p6q7 = 3q
(iii) – 21m5n7 by 14m2n2
– 21m5n7 ÷ 14m2n2 = (- 21 × m5 × n7) / (14 × m2 × n2)
This can be written as,
= (- 3 × 7 × m5-2 × n7-2) / (2 × 7)
= (- 3 × m3 × n5) / 2
We get,
= – 3m3n5 / 2
Hence, – 21m5n7 ÷ 14m2n2 = – 3m3n5 / 2
(iv) 36a4x5y6 by 4x2a3y2
36a4x5y6 ÷ 4x2a3y2 = (36 × a4 × x5 × y6) / (4 × x2 × a3 × y2)
This can be written as,
= (4 × 9 × a4-3 × x5-2 × y6-2) / 4
= 9 × a1 × x3 × y4
We get,
= 9ax3y4
Hence, 36a4x5y6 ÷ 4x2a3y2 = 9ax3y4
(v) 20x3a6 by 5xy
20x3a6 ÷ 5xy = (20 × x3 × a6) / (5 × x × y)
This can be written as,
= (4 × 5 × x3-1 × a6) / (5 × y)
We get,
= (4 × x2 × a6) / y
= 4x2a6 / y
Hence, 20x3a6 ÷ 5xy = 4x2a6 / y
4. Simplify:
(i) (- 15m5n2) / (- 3m5)
(ii) 35x4y2 / – 15x2y2
(iii) (- 24x6y2) / (6x6y)
Solution:
(i) (-15m5n2) / (- 3m5) = (-15 × m5 × n2) / (- 3 × m5)
This can be written as,
= (3 × 5 × m5-5 × n2) / 3
= 5 × m0 × n2
= 5 × 1 × n2
= 5n2
Hence, (-15m5n2) / (- 3m5) = 5n2
(ii) 35x4y2 / – 15x2y2
35x4y2 / – 15x2y2 = (35 × x4 × y2) / (- 15 × x2 × y2)
This can be written as,
= – (5 × 7 × x4-2 × y2-2) / (3 × 5)
= – (7 × x2 × y0) / 3
We get,
= – 7x2y / 3
Hence, 35x4y2 / – 15x2y2 = – 7x2y / 3
(iii) (- 24x6y2) / (6x6y)
(- 24x6y2) / (6x6y) = (- 24 × x6 × y2) / (6 × x6 × y)
This can be written as,
= (- 4 × 6 × x6-6 × y2-1) / 6
= – 4 × x0 × y1
= – 4y
Hence, (- 24x6y2) / (6x6y) = – 4y
5. Divide:
(i) 9x3 – 6x2 by 3x
(ii) 6m2 – 16m3 + 10m4 by – 2m
(iii) 15x3y2 + 25x2y3 – 36x4y4 by 5x2y2
(iv) 36a3x5 – 24a4x4 + 18a5x3 by – 6a3x3
Solution:
(i) 9x3 – 6x2 by 3x
9x3 – 6x2 ÷ 3x = (9 × x3 – 6 × x2) / (3 × x)
Separating the terms, we get
= (9 × x3) / (3 × x) – (6 × x2) / (3 × x)
We get,
= 3 × x3-1 – 2 × x2-1
= 3x2 – 2x
Hence, 9x3 – 6x2 ÷ 3x = 3x2 – 2x
(ii) 6m2 – 16m3 + 10m4 by – 2m
6m2 – 16m3 + 10m4 ÷ – 2m = (6 × m2– 16 × m3 + 10 × m4) / – 2 × m
Separating the terms, we get
= (6 × m2 / – 2 × m) – (16 × m3) / (- 2 × m) + (10 × m4) / (- 2 × m)
= – 3 × m2-1 + 8 × m3-1 – 5 × m4-1
= – 3 × m + 8 × m2 – 5 × m3
We get,
= – 3m + 8m2 – 5m3
Hence, 6m2 – 16m3 + 10m4 ÷ – 2m = – 3m + 8m2 – 5m3
(iii) 15x3y2 + 25x2y3 – 36x4y4 by 5x2y2
15x3y2 + 25x2y3 – 36x4y4 ÷ 5x2y2 = (15x3y2 + 25x2y3 – 36x4y4) / (5x2y2)
= (15 × x3 × y2) / (5 × x2 × y2) + (25 × x2 × y3) / (5 × x2 × y2) – (36 × x4 × y4) / (5 × x2 × y2)
On further calculation, we get
= 3 × x3-2 × y2-2 + 5 × x2-2 × y3-2 – (36 × x4-2 × y4-2) / 5
We get,
= 3 × x1 × y0 + 5 × x0 × y1 – (36 × x2 × y2) / 5
= 3x + 5y – (36x2y2) / 5
Hence, 15x3y2 + 25x2y3 – 36x4y4 ÷ 5x2y2 = 3x + 5y – (36x2y2) / 5
(iv) 36a3x5 – 24a4x4 + 18a5x3 by – 6a3x3
36a3x5 – 24a4x4 + 18a5x3 ÷ (– 6a3x3) = (36a3x5 – 24a4x4 + 18a5x3) / – 6a3x3
= (36.a3.x5) / (-6.a3.x3) – (24.a4.x4) / (-6.a3.x3) + (18.a5.x3) / (-6.a3.x3)
We get,
= – 6.x5-3 + 4.a4-3.x4-3 – 3.a5-3
= – 6x2 + 4ax – 3a2
Hence, 36a3x5 – 24a4x4 + 18a5x3 ÷ (– 6a3x3) = – 6x2 + 4ax – 3a2
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