NCERT Solutions For Class 7 Maths Chapter 11 Exercises
- NCERT Solutions For Class 7 Maths Chapter 11 Perimeter and Area Exercise 11.1
- NCERT Solutions For Class 7 Maths Chapter 11 Perimeter and Area Exercise 11.2
Exercise 11.1
Q1. Find
(a) the area of the land
(b) the price of the land,
If the land is of rectangular shape measuring 300 m in length and 400 m in breadth. The cost of 1m^{2} land is Rs. 10000.
Ans: (a) Area = Length (l) x Breadth (b)
= 300 x 400
= 120000 m^{2}
(b) Cost of 1 m^{2} land = Rs 10000
Cost of 120000 m^{2 }land = 10000 x 120000 = Rs 1200000000.
Q2. The perimeter of a park is 240m. Determine the area.
Ans: Perimeter = 240 m
4 x Length of a side of the park = 240
Length of a side of park = 240/4 = 60 m
Area = (Length of a side of park)^{ 2} = (60)^{2} = 3600 m^{2 }
Q3. The area and length of a rectangular plot of land are 1200 m^{2} and 40 m respectively. Determine its perimeter.
Ans: Area = Length (l) x Breadth (b) = 1200 m^{2}
= 40 x Breadth = 1200
= Breadth = 1200/40 = 30
Perimeter = 2 (Length (l) + Breadth (b) )
= 2 (30 + 40) = 2 (70) = 140 m
Q4. Find the breadth and area if the perimeter and length of the rectangular sheet is 120 cm and 40 cm respectively.
Ans: Perimeter = 2 (Length + Breadth) = 120 cm
2 (40 + Breadth) = 120
40 + b = 60
b = 6O – 40 =20 cm
Area = Length (l) x Breadth (b) = 40 x 20 = 800 cm^{2}
Q5. The area of the rectangular park is equal to a square park. If the length of rectangular park measures 80m and the side of the square park is 100 m .Determine the breadth of the rectangular park.
Ans: Area of the square park = (side of the park)^{2} = (100)^{2} = 10000 m^{2}
Area of the rectangular park = Length (l) x Breadth (b) = 10000
80 x Breadth = 10000
Breadth = 125 m
Q6. The length and breadth of a wire whose shape is a rectangle are 22 and 40 respectively. The wire is then reshaped into a square. Determine the side of the square and find out which shape encloses more area.
Ans: Perimeter of the rectangle = Perimeter of the square
2 (Length (l) + Breadth (b)) = 4 x Side
2 (22 + 40) = 4 x Side
2 x 62 = 4 x Side
Side =124/4 = 31 cm
Area of the rectangle = 22 x 40 = 880 cm^{2}
Area of the square = (Side)^{2} = 31 x 31 = 961 cm^{2}
Therefore, the square shaped wire encloses more area.
Q7. If the breadth and perimeter of a rectangle are 40 cm and 120 cm respectively, determine the length and area of the rectangle.
Ans: Perimeter = 2 (Length (l) + Breadth (b)) = 120
2 (Length + 40) = 120
Length + 40 = 60
Length = 60 – 40 = 20 cm
Area = Length (l) x Breadth (b) = 20 x 40 = 800 cm^{2}
Q8. A door is fitted in a wall whose length measures 1 m and breadth measures 2 m. The length and breadth of the wall are 5 m and 3.5 m (in the given figure). The price of white washing the wall is Rs 10 per m^{2}. Find the cost of whitewashing the wall without the door.
Ans: Area of the wall = 5 x 3.5 = 17.5 m^{2}
Area of the door = 2x 1 = 2 m^{2}
Area to be white-washed = 17.5 – 2 = 15.5 m^{2}
Cost of white-washing 1 m^{2} area = Rs 10
Cost of white-washing 15.5 m^{2} area = 15.5 x 10 = Rs 155
Exercise 11.2
Q1. Determine the area of the parallelograms in the diagram given below
Ans:
(a) Area of a parallelogram = Height x Base
Base = 8 cm
Height = 5 cm
Area = 8 x 5 = 40 cm^{2}
(b) Area of a parallelogram = Height x Base
Base = 6 cm
Height = 4 cm
Area = 6 x 4 = 24 cm^{2}
(c) Area of a parallelogram = Height x Base
Base = 4.5 cm
Height = 7 cm
Area = 4.5 x 7 = 31.5 cm^{2}
(d) Area of a parallelogram = Height x Base
Base = 9.6 cm
Height = 10 cm
Area = 9.6 x 10 = 96 cm^{2}
(e) Area of a parallelogram = Height x Base
Base = 8.8 cm
Height = 4 cm
Area = 8.8 x 4 = 35.2 cm^{2}
Q2. Determine the area of the triangles .
Ans:
(a) Area of a triangle
Height = 6 cm
Base = 8 cm
Area
(b) Area of a triangle
Height = 6.4 cm
Base = 10 cm
Area
(c) Area of a triangle
Height = 6 cm
Base = 8 cm
Area
(d) Area of a triangle
Height = 4 cm
Base = 6 cm
Area
Q3. Fill the empty cells:
S. No | Base | Height | Area of parallelogram |
A | 10 cm | 124 cm^{2} | |
B | 12 cm | 96 cm^{2} | |
C | 7 cm | 91 cm^{2} | |
D | 11 cm | 121 cm^{2} |
Ans:
(a) Area of a parallelogram = Height x Base
B = 10 cm
H =?
Area = 124 cm^{2}
10 x h = 124
So, the height of the parallelogram is 12.4 cm
(b) Area of a parallelogram = Height x Base
B =?
H = 12 cm
Area = 96 cm^{2}
b x 12 = 96
So, the base of the parallelogram is 8 cm
(c) Area of a parallelogram = Height x Base
B = 7 cm
H =?
Area = 91 cm^{2}
7 x h = 91
So, the height of the parallelogram is 13 cm
(d) Area of a parallelogram = Height x Base
B = 11 cm
H =?
Area = 121 cm^{2}
11 x h = 121
So, the height of the parallelogram is 11 cm
Q4. Fill in the blanks:
Base | Height | Area of triangle |
12 | 24 cm^{2} | |
30 | 60 cm^{2} | |
22 | 66 cm^{2} |
Ans:
(a) Area of a triangle
Height = ?
Base = 12 cm
Area
Therefore, the height of the triangle is 4 cm
(b) Area of a triangle
Height = 30 cm
Base = ?
Area
Therefore, the base of the triangle is 4 cm
(c) Area of a triangle
Height =?
Base = 22 cm
Area
Therefore, the height of the triangle is 6 cm.
Q5. ABCD is a parallelogram (in the given figure). BX is the height from B to CD and BY is the height from B to AD. If CD = 12 cm and BX = 7.6 cm.
Find: (a) the area of the parallelogram ABCD
(b) BY, if AD = 8 cm.
Ans:
(a) Area of parallelogram = Base x Height = CD x BX
= 7.6 x 12 = 91.2 cm^{2}
(b) Area of parallelogram = Base x Height = AD x BY = 91.2 cm^{2}
BY x 8 = 91.2
BY = 91.2/8 =11.4 cm
Q6. SL and QM are the heights on sides PQ and PS respectively of parallelogram PQRS (in the given figure). If area of parallelogram is 1470 cm^{2}, AB = 35 cm and AD = 49 cm, find the length of BM and DL.
`Ans:
Area of a parallelogram = Height x Base = PQ x SL
1470 = 35 x SL
DL =
Also, PS x QM = 1470
1470 = 49 x QM
Q7. ABC is right angled at A (in the given figure). AD Is perpendicular to BC. If AB = 5 cm, BC = 13 cm and AC = 12 cm, determine the area of triangle ABC. Also find the length of AD.
Ans:
Area of a triangle
Also, area of triangle
AD = 4.6 cm
Q8. Triangle ABC is isosceles with AB = AC = 7.5 cm and BC = 9 cm (in the given figure). The height AD from A to BC is 6 cm. Find the area of triangle ABC. What will be the height from C to AB i.e., CE?
Ans:
Area of triangle ABC
Area of triangle ABC
CE = 7.2