The circumference of every circle is (pi) times (diameter).
The diameter is (2 x radius), so we can write
Circumference = (pi) x (2 x radius) .
The question gives us the circumference, and the number to use for (pi).
I shall now pluggum in:
(31.4 cm) = (3.14) x (2 x radius)
Divide each side by 3.14: (31.4 cm)/(3.14) = 2 x radius
Divide each side by 2 : (31.4 cm) / (2 x 3.14) = radius
5 cm = radius
