If you open math book you will find a lot of mathematical
questions but you should have solve this question.
It is from class 10 rd sharma chapter 15.4 mensuration .
In this question we have to find the the area of the shaded
region and the length of the boundary of the shaded region
given that ABCD is rectangle, having AB = 20 cm and BC = 14 cm.
Two sectors of 180° have been cut off.
Given,
Length of the rectangle = AB = 20 cm
Breadth of the rectangle = BC = 14 cm
(i) Area of the shaded region = Area of rectangle – 2 x Area of the semi-circle
= l x b – 2 x ½ πr2
= 20 x 14 – (22/7) x 72
= 280 – 154
= l26 cm2
(ii) Length of the boundary of the shaded region = 2 x AB + 2 x circumference of a semi-circle
= 2 x 20 + 2 x πr
= 40 + 2 x (22/7) x 7
= 40 + 44
= 84 cm