Multiple choice

On increasing the radius of circle by 1 cm, its area is increased by 44 cm2 .The original radius of the circle is - एक वृत्त की त्रिज्या में 1 सेमी. की वृद्धि करने पर इसका क्षेत्रफल 44 सेमी.2 बढ़ जाता है। वृत्त की मूल त्रिज्या है-

  1. 5.6 cm./सेमी.

  2. 6.5 cm./सेमी.

  3. 6 cm./सेमी.

  4. 9 cm./सेमी.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let original radius be r cm. Area = πr². New area = π(r+1)² = π(r² + 2r + 1). The increase is π(r² + 2r + 1) - πr² = π(2r + 1) = 44. Using π = 22/7: (22/7)(2r + 1) = 44, so 2r + 1 = 14, giving r = 6.5 cm.

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