Question

A circle of radius 10cm had a hole cut out of its centre to form a ring. Find the radius of the hole if the remaining area is 50% of the original area. Round to one decimal place

Answer 1

7.07cm

Explanation:

A=πr2

= 100 π

= 314.159265359/2 (squared)

50% = 157.07963268cm ^2

We look for radius in the area formula

A=πr2

(A / π ) = 157.07963268/ 3.14159265359 = √50 = 7.07106781187

We do not need to half this as already has been squared.