Multiple choice

A certain sum amounts to Rs.$ 17,700$ in $3$ years and Rs. $20,400$ in $6$ years under simple interest. Find the sum and rate of interest.

  1. $Rs. 15,000, 10$% p.a.
  2. $Rs. 15,000, 6$% p.a.
  3. $Rs. 10,000, 5$% p.a.
  4. $Rs. 12,500, 10$% p.a.
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B Correct answer
AI explanation

Under simple interest, the difference in the amounts over equal periods represents the interest for that period, so the interest for 3 years is 20400 - 17700 = Rs. 2700. This means the interest for one year is 2700 / 3 = Rs. 900, making the interest for the first three years total Rs. 2700. The original principal is the 3-year amount minus this interest, which is 17700 - 2700 = Rs. 15000. Using the simple interest formula, the rate is calculated as R = (900 * 100) / 15000 = 6% p.a.

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