Multiple choice

The simple interest on a certain sum at 5% per annum for 3 years and 4 years difference by Rs. 42. The sum is-

  1. Rs. 210

  2. Rs. 280

  3. Rs. 750

  4. Rs. 840
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Simple Interest for 3 years = P × 5% × 3 = 0.15P. Simple Interest for 4 years = P × 5% × 4 = 0.20P. The difference is 0.20P - 0.15P = 0.05P, which equals Rs. 42. Therefore, P = 42 / 0.05 = Rs. 840. The key insight is that the difference in interest for consecutive years at simple interest is just the interest for one year.

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