Multiple choice

There are two concentric circle whose areas are in the ratio of 9 : 16 and the difference between their diameter is 4 cm. What is the area of the outer circle? दो संकेन्द्री वृत्त है जिनके क्षेत्रफलों का अनुपात 9 : 16 है और उनके व्यास का अन्तर 4 सेमी. है। बाहरी वृत्त का क्षेत्रफल क्या है?

  1. 32 π cm2/सेमी2

  2. 64 π cm2/सेमी2

  3. 36 π cm2/सेमी2

  4. 48 π cm2/सेमी2
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B Correct answer
Explanation

Area ratio 9:16 means radius² ratio is 9:16, so radius ratio is 3:4. Let radii be 3r and 4r. Difference in diameters = 2(4r-3r) = 2r = 4cm, so r = 2cm. Outer radius = 4r = 8cm. Area = π(8)² = 64π cm².

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