Question

The two circles have different diameters in the ratio 5:3.

(A) Calculate the radius of circle B if circle A has a radius of 35mm

(B) Calculate the area of circle A giving your answer to the nearest cm squared.

Answer 1

a) 21 mm

b) 39 cm^2

Explanation:

a) The ratio of the diameter from A to B is 5:3

Let the diameter of B be x

If 35 is the radius of A, then its diameter is 35 * 2 = 70 mm

Thus;

5/3 = 70/x

5* x = 70 * 3

5x = 210

x = 210/5

x = 42 mm

So the radius of circle B will be 42/2 = 21 mm

b) The area of circle A

Mathematically we apply the area of a circle formula here

A = pi * r^2

A = 22/7 * 35 * 35

A = 3,850 mm^2

To convert this to cm^2, we will

need to divide by 100

That would be 3850/100 = 38.5 cm^2 = 39 cm^2