Multiple choice

The simple interest on a certain sum for 8 months at 4% per annum is 129 less than the simple interest on the same sum for 15 months at 5% per annum. The sum is- एक धनराशि पर 4% वार्षिक ब्याज की दर से 8 माह का साधारण ब्याज उसी धनराशि पर 15 माह के लिए 5% वार्षिक ब्याज की दर से साधारण ब्याज से 129 कम है । धनराशि है-

  1. 2580

  2. 2400

  3. 2529

  4. 3600
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let sum = P. SI at 4% for 8 months = P × 4 × 8/100 × 12 = 8P/2400. SI at 5% for 15 months = P × 5 × 15/100 × 12 = 75P/2400. Difference: 75P/2400 - 8P/2400 = 67P/2400 = 129. Solving: P = 129 × 2400/67 = 3600. Therefore, the sum is Rs. 3600.

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