S.chand publication New Learning Composite mathematics solution of class 7 Chapter 14 Perimeter and Area Exercise 14C

 Exercise 14C

Question 1

Find the area of the following parallelogram

(a)

Figure to be added

Area of parallelogram=(base×altitude)

=(5×4) cm²

=20

(b)

Figure to be added

Area of parallelogram=(base×altitude)

=(12×9) cm²

=108

(c)

Figure to be added

Area of parallelogram=(base×altitude)

=(15×7.5) cm²

=112.5

Question 2

Use the area of the parallelograms to find their missing base b of height h

(a) A=88 cm^{2 ,}b=11 cm, h=?

Area=base×height

88=11×h

$h=\frac{88}{11}=8$

∴h=8

(b) A=126 cm^{2 ,}b=? cm, h=9 m

Area=base×height

126=b×9

$b=\frac{126}{9}$

b=14

Question 3

The area of a parallelogram is 216 sq cm and the base is 6 times the height. Find the parallelogram's height

Let, the height be h

ATQ,

216=6h×h

216=6h²

h²$=\frac{216}{6}$

∴h=6

Ans : Height of the parallelogram is 6 cm

Question 4

The area of a parallelogram in a stained glass window is 120 sq cm and the height is 10 cm. What is the base?

Area of parallelogram=base×height

120=b×10

$b=\frac{120}{10}$

∴b=12

Ans : Base of the parallelogram is 12 cm

Question 5

Find the shaded area. All measurements are in centimetres 

Figure to be added

Area of the ▭=(80×60)=4800 cm²

Area of the parallelogram=(55×45)=2475 cm²

∴The shaded area=(4800-2475)cm² 

=2325

Question 6

A lawn is in the shape of a parallelogram the base is 50 m and the height is 18m. You can plant 15 sq m of grass per minute. How long will it take you to plant the lawn?

∴Area of the lawn=(50×18) m² 

=900 m² 

We can plant 15 sq  m of grass per minute

∴Total time to plant the lawn$=\frac{900}{15}$ min

=60 min

=1 hour

Ans : It takes 1 hour to plant the lawn

Question 7

The area of a rhombus is 60 m² . If its perimeter is 40 m.Find its altitude

∴Side of the rhombus$=\frac{40}{4}$ m

=10 m

Area of rhombus=side×altitude

60=10×altitude

altitude$=\frac{60}{10}=6$