Ncert Solutions For Class 7 Maths Ex 4.3

Ncert Solutions For Class 7 Maths Chapter 4 Ex 4.3

 

 Q-1) Set up the equations and solve them to find the unknown numbers in the cases given below:

  1. If you add 6 to five times a number, it gives 46.
  2. Two-third of a number minus 5 gives 11.
  3. If you take one-third of a number and add 4 to it, gives 45.
  4. When person X subtracts 12 from thrice of a number, it gives 18.
  5. When Jenny subtracts twice the number of pens she has from 40, she gets 16.
  6. Virat guesses a number. If he adds 18 to that number and then divides the sum by 6, he gets answer 7.
  7. Ami guesses a number. If she subtracts 8 from two-third of a number, she gets 6.

Ans.)

1) Say, m is the required number.

Therefore, five times a number = 5m

Thus, from the given statement,

5x + 6 = 46

5x = 46 – 6

5x = 40

x = 40/5

x = 8

 

2) Say, n is the required number.

Therefore, Two-third of a number = 2n/3

Thus, from the given statement,

2n/3 – 5 = 11

2n/3 = 11 + 5

2n/3 = 16

2n = 16*3

2n = 48

n = 48/2

n = 24

 

3) Say, n is the required number.

Therefore, One-third of a number = n/3

Thus, from the given statement,

n/3 + 4 = 45

n/3 = 45 – 4

n/3 = 41

n = 41*3

n = 123

 

4) Say, k is the required number.

Therefore, Thrice of a number = 3k

Thus, from the given statement,

3k – 12 = 18

3k = 18 + 12

3k = 30

k = 30/3

k = 10

 

5) Let jenny has x numbers of pen,

Therefore, Twice the number of pens = 2x

Thus, from the given statement,

40 – 2x = 16

40 = 2x + 16

40 – 16 = 2x

2x = 40 – 46

2x = 24

x = 12

 

6) Say, Virat guesses a number ‘a’.

Thus, from the given statement,

(a + 18) / 6 = 7

a + 18 = 7*6

a + 18 = 42

a = 42 – 18

a = 24

 

7) Say, ami guesses a number ‘a’.

Therefore, Two-third of a number = 2a/3

Thus, from the given statement,

2a/3 – 8 = 6

2a/3 = 6 + 8

2a/3 = 14

2a = 14*3

2a = 42,

a = 21

 

Q-2) Solve the following:

  1. The teacher noticed that in a Class of standard 7th, the highest marks obtained in the class is thrice the lowest marks plus 4. The highest mark is obtained by Karan and is 91. If Kishan has got the lowest score, what is his mark?
  2. In an isosceles triangle, all the base angles are equal. Vertex angle is given as 50. Find the measure of base angle of an isosceles triangle.( Sum of all the interior angles of a triangle is 180)
  3. Virat scored thrice the number of runs scored by Rohit. The sum of their scores fall 4 short of a triple century. Find the individual scores of Virat and Rohit.

Ans.)

1) Say, Kishan scored ‘m’ marks (lowest marks)

Karan scored 91 marks (highest marks)

From the statement given in the question,

3m + 4 = highest marks

3m + 4 = 91

3m = 91 – 4

3m = 87

m = 87/3

m = 29

Thus, Kishan scored 29 marks.

 

2) Let, the base angle be x.

Vertex angle = 50

Sum of all the interior angles of a triangle is 180

 x + x + 50 = 180

 2x = 18050

 2x = 130

 x = 130/2

 x = 65

 

3) Let Rohit’s scored ‘m’ runs

Virat scored thrice runs then that of Rohit   = 3m

Here, the sum of their scores falls 4 short of triple century.

So, 3m + m = 300 – 4

4m = 296

m = 296/4

m = 74

Rohit score = m = 74

Virat’s score = 3m = 3(74) = 232

So, Virat scored 232 runs and Rohit scored 74 runs.

 

Q-3) Solve the following:

  1. Umesh says that he has 5 toffies more than 6 times the number of toffies Shami has. Umesh has 47 toffies. Calculate the number of toffies that Shami has? (Say, xis the number of toffies with the Shami).
  2. John’s father is 59 years old. He is 3 years older than 4 times John’s age. What is the age of John (Say, John is yyears old at present.)?
  3. Trees were planted by the people of Bengaluru city in the ‘Lalbagh Garden’. Some trees are fruit trees while some were not. The number of fruit trees is three less than four times the number of non- fruit trees. Calculate the number of non-fruit trees planted if the number of fruit trees planted was 65.

Ans.)

1) Let Shami has x toffies.

Therefore, Six times the toffies of shami = 6x

Here, Umesh says that he has 5 toffies more than 6 times the toffies Shami has.

So, 6x + 5 = 47

6x = 47 – 5

6x = 42

x = 42/6

x = 7

So, Umesh has 7 toffies.

 

2) Let John be y years old.

Therefore, 4 times John’s age = 4y

Here, John is 3 years older than 4 times John’s age.

So, 4y + 3 = 59

4y = 59 – 3

4y = 56

y = 14

Thus, John is 14 years old.

 

3) Let the m be the number of non-fruit trees.

Therefore, 4 times the number of non-fruit tress is = 4m

Number of fruit trees planted = 65.

Here, the number of fruit trees is three less than four times the number of non- fruit trees.

4m – 3 = 65

4m = 65 + 3

4m = 68

m = 68/4

m = 17

Thus, the number of non-fruit trees is 17.

 

Q-4) Solve the riddle given below:

“I am a Number,

Tell me my identity!

Take me nine times over

And subtract forty!

To reach a Double century

You still need sixty!

 Ans.)  Let the required number be p.

As per the given riddle

(9p – 40) + 60 = 200

(9p – 40) = 200 – 60

(9p – 40) = 140

9p = 140 + 40

9p = 180

p = 180/9

p = 20

So, the identity of the number is 20.