Question

area enclosed between circumference of two concentric circle is 16π sq cm and their radii are in the ratio 5:3 . what is area of outer circle? ( use π = 3.14)

Answer 1

Please see the attachment

Answer 2

Given,

Radius of Outer circle : Radius if Inner circle = 5:3

Therefore, Let Radius of Outer circle = 5k

and Radius if Inner circle = 3k

Given,

Area of Outer circle - Area of Inner circle = 16π sq cm

=> π(5k)² - π(3k)² = 16π

=> 25k² - 9k² = 16                 [π is cancelled out]

=> 16 k² = 16

=> k² = 1

=> k = 1, -1

but radius cannot be negative, therefore k = 1

∴ Radius of Outer circle = 5x1 cm = 5 cm

∴ Area of Outer circle = π (5)² = 3.14 x 25 = 78.5 sq cm