Question

The area enclosed between two concentric circles of
radii 5 cm and 10 cm is the same as between the third
and the second concentric circle. Find the total area of
the third circle.

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Answer 1

Answer:

total area of the 3rd ring = area of 1st ring + area between 1st and 2nd ring + area between 2nd and 3rd ring

area of 1st ring = π(r1)²

=> π(5²)

=> 25π ..........1

area between the 1st and 2nd ring =>

=> π [ (r2)² - (r1)² ]

=> π (10² - 5²)

=> π ( 100 - 25)

=> 75π .................2

area between 2nd and 3rd ring is same as area between 1st and 2nd ring = 75π ..........3

therefore total area of 3rd circle = 1+2+3

=> 25π + 75π + 75π

=> 175π

=> 175 × 22/7

=> 550 cm²