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Railways PYQCBT 1 2016

RRB NTPC · Question 18

The simple interest on a certain sum of money invested at a certain rate for 2 years is Rs 1200. The compound interest of the same sum of money invested at the same rate of interest for 2 years is Rs 1290. What was the principal? A. Rs. 12000 B. Rs. 16000 C. Rs. 6000 D. Rs. 4000

  1. C

  2. A

  3. D

  4. B

Show answer & explanation

Answer: (C) D

Explanation

SI for 2 years = 1200, so the yearly interest = Rs 600. The CI exceeds the SI by 1290 − 1200 = Rs 90, which is the interest on the first year's interest: 600 × r/100 = 90, so r = 15%. Principal = 600 × 100/15 = Rs 4,000 (check: 4000 × 15% × 2 = 1200).