Q26 of 35 Page 311

The inner diameter and external diameter of an Iron ring plate are 20 cm and 22 cm. The quality of iron plate in the ring is


Given: Inner diameter = 20 cm


Outer diameter = 22 cm


⇒ Inner radius = 10 cm and outer radius = 11 cm


Area of such concentric circles = Area of the larger circle – area of the smaller circle


∵The area of a circle = πr2


⇒ Area of the iron plate = πR2 - πr2


⇒ Area of the iron plate


⇒ Area of the iron plate


⇒ Area of the iron plate


⇒ Area of the iron plate


⇒ Area of the iron plate = 22× 3 = 66cm2

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