Multiple choice

A person invested a sum of ₹18,600 at (x)% p.a. and another sum that is twice the former at (x+2)% p.a., both at simple interest. If the total interest earned on both investments for 3 (1/2) years is ₹23,110.50, then the rate of interest p.a. on the second investment is:

  1. 12.5%

  2. 8%

  3. 6.5%

  4. 20%
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A Correct answer
Explanation

First investment: ₹18,600 at x% for 3.5 years = ₹18,600 × 3.5x/100. Second investment: ₹37,200 at (x+2)% for 3.5 years = ₹37,200 × 3.5(x+2)/100. Total interest = ₹651x + ₹1302(x+2) = ₹23,110.50. Solving: 1953x + 2604 = 23110.50, so 1953x = 20506.50, x = 10.5. Second investment rate = x + 2 = 12.5%.

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