Question

find the radius of circumcircle is 57.2 CM

Answer 1

circumference of a circle= 2×pi×r
57.2cm= 2×22/7 × radius
57.2 cm ×7 = 44 × radius
400.4cm/44 = radius
radius= 9.1 cm

check: 
2× pi×r
2×22/7×9.1
=57.2 cm^2

Answer 2

circumference = 57.2 CM

$c \: = 2\pi \:r \:$


$2 \times \frac{22}{7} \times 57.2$

$\frac{57.2}{22} = 2.6 \\ = 2.6 \times 7 = 18.2$