Question

Find the area of circle if it's diameter 42cm

Answer 1

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d=42
r=21
area of circle is pi r^2
22/7×21×21
=1386 cm^2
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this is area of circle

Answer 2

r=1/2d
=1/2×42
=21cm
$a = \pi {r}^{2}$
a=22/7×21×21
=22/7×441
=22×63
=1386cm