A circular mat has a circumference of 200. Find the radius rounded to the nearest whole number?

The formula to calculate a circumference of a circle is:
circumference = π x diameter of the circle (D)

so

200 = π x D

rearranging

D = 200/π

π is a constant equal to approx 3.14

D = 200/3.14

D = 63.69

So if the diameter of the circle is 63.69, then the radius is half of this figure, so the radius is 31.85, or 32 rounded to the nearest whole number.