Question

find the area of semicircle ( diameter of full circle is 10cm)

Answer 1

Area = πr²/2
r=d/2
=10/2
=5

Answer 2

Area of full circle
$= \pi {r}^{2}$
$= 3.14 \times {5}^{2}$
$= 3.14 \times 25$
$= 78.5$
Area of half circle

$= 78.5 \div 2$
$= 39 .25$
Your answer depends on the value of pi. But approx. answer will be same.