#### Question

The area enclosed between the concentric circles is 770cm2. If the radius of outer circle 21cm. find the radius of inner circle

#### Solution

Radius of outer circle = 21𝑐𝑚

Radius of inner circle = 𝑅_{2}

Area between concentric circles = area of outer circle – area of inner circle

⇒ 770 =`22/7`(21^{2} − R_{2}^{2})

⇒ 21^{2} − 𝑅_{2}^{2} = 35 × 7 = 245

⇒ 441 – 245 = 𝑅_{2}^{2}

⇒𝑅_{2}= `sqrt(196)` = 14 𝑐𝑚

Radius of inner circle = 14cm.

Is there an error in this question or solution?

#### APPEARS IN

Solution The Area Enclosed Between the Concentric Circles is 770cm2. If the Radius of Outer Circle 21cm. Find the Radius of Inner Circle Concept: Areas of Combinations of Plane Figures.