Question

The area of circular ring enclosed between two concentric circles is 572 square cm. Find the radii of the two circles, given that their difference is 7 cm

Answer 1

Answer:

Area of outer circle - area of inner circle = 286 sqcm

Pi(r1² - r2²) = 286 sqcm

Pi(r1 - r2) (r1 + r2) = 286

Pi × 7 × (r1 + r2) = 286

r1 + r2 = 286/22= 13

Now by solving 2 equations simultaneously

r1 + r2 = 13

r1 - r2 = 7

You get r1 = 10cm, r2=7 cm