Question

pls answer question no.21

Answer 1

OA=OB  r given

perimeter of the shaded region =circumference of the semicircle APB+circumference of AQO

then 40= pie r+pie r/2

then 80= 3 pie r

then r =80/3 pie      .......(1)

now the area shaded region  pie r^2+ pie( r /2)^2 = (5 pier^2) /4

now  put the value of r from (1)

283.09cm^2

Answer 2

your answer is

$283.09 {cm}^{2}$