Question

the area enclosed by the circumference of two concentric circles is 16πsq.cm and their radii are in the ratio5 : 3 .what is the area of the outer circle (use π = 3.14)​

Answer 1

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Step-by-step explanation:

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

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