Discuss Forum
1.
The difference between the radii of bigger circle and smaller circle is 14 cm and the difference between their areas is 1056 cm2 . Radius of the smaller circle is _
- A. 7 cm
- B. 7 cm
- C. 7 cm
- D. 7 cm
Answer: Option B
Explanation:
Let the radius of the smaller circle be r cm
Then, radius of bigger circle = (r + 14)cm
Given, π(r + 14) 2−π(r) 2 = 1056
⇒ π(r 2 + 28r + 196)−πr 2 = 1056
⇒πr 2 + 28πr + 196π−πr 2 = 1056
⇒28 × 22/ 7 + 196x22/ 7 = 1056
= >88r + 616 = 1056
⇒r = 5 cm.
Then, radius of bigger circle = (r + 14)cm
Given, π(r + 14) 2−π(r) 2 = 1056
⇒ π(r 2 + 28r + 196)−πr 2 = 1056
⇒πr 2 + 28πr + 196π−πr 2 = 1056
⇒28 × 22/ 7 + 196x22/ 7 = 1056
= >88r + 616 = 1056
⇒r = 5 cm.
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