Multiple choice

A sum amounts to Rs.11638 in 2 years and to Rs.13383.7 in 3 years compounded annually. Find the sum and the rate of interest per annum. एक धनराशि चक्रवृद्धि ब्याज की दर से 2 वर्षों में 11638 रु. और 3 वर्षों में 13383.7 रु. हो जाती है | धनराशि और प्रति वर्ष ब्याज की दर ज्ञात कीजिये |

  1. Rs. /रु.8250, 15%

  2. Rs. /रु.8550, 12%

  3. Rs. /रु.8880, 18%

  4. Rs. /रु.8800, 15%
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D Correct answer
Explanation

Let P be principal, r be rate. P(1 + r/100)² = 11638 and P(1 + r/100)³ = 13383.7. Dividing: 1 + r/100 = 13383.7/11638 = 1.15, so r = 15%. Substituting back: P = 11638/(1.15)² = 11638/1.3225 = 8800. Verify: 8800 × 1.3225 = 11638 ✓ and 8800 × 1.520875 = 13383.7 ✓.

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