Question

10. The difference of areas of two circles is 100 cm and the difference of their perimeters is 10 cm. The sum of their radii is (a) 207t cm (b) 20 cm (c) 10/2 cm (d) 10T cm Ans. (b)​

Answer 1

Answer:

Ans. 20 cm

Step-by-step explanation:

let the two circles are circle and circle B

Area of circle A =πr1²

Area of circle B=πr2²

(radius of A is r1

radius of B is r2)

Difference in the areas=π(r1)²-π(r2)²=100 cm

Difference in perimeters = 2π(r1) - 2π(r2) =10cm

r1²-r2²/2r1-2r2=100/10

10(r1+r2) (r1-r2) =2×100(r1-r2)

200/10=(r1+r2)

r1+r2 = 20 cm