Question

solve the Q. pls proper solution​

Answer 1

Answer:

14cm

Step-by-step explanation:

let the radius of inner circle be (r) and outer circle be (R)

area between concentric circles  = area of outer circle - area of inner circle

                  770 cm^2 =  \pi R^2 - \pi r^2

                                  = (22/7 * 21^2)cm^2 - (22/7 * r^2)cm^2

                    = 1386cm^2     -(22/7 * r^2)cm^2

770cm^2 - 1386cm^2 = -(22/7 * r^2)cm^2

-616cm^2 =- (22/7 * r^2)cm^2

616 = 22/7 * r^2

616*7/22 = r^2

196 = r^2

r = 196^1/2 = 14cm

Answer 2

Answer:

Radius = 14cm

Step-by-step explanation:

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