Quantitative Aptitude

Simple and Compound Interest

3,394 Questions
All Simple interest and its inverse forms 768 Compound interest with annual compounding 742 Simple-interest growth and split sums 626 Difference between compound and simple interest 479 Half-yearly and quarterly compounding 252 Changing rates and fractional years 201 Installments (CI based) 190 Ratio of principal to interest 118 Population growth and depreciation 16

Simple and Compound Interest Questions

Multiple choice

A sum of Rs 1,200 was lent partly at 5% and partly 6% simple interest. The total interest received after 2 years was Rs 128. The ratio of the money lent out at 5% and 6% is

  1. 5:6

  2. 6:5

  3. 2:1

  4. 1:2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let x be amount at 5% and y be amount at 6%. x + y = 1200. Interest = (x * 0.05 * 2) + (y * 0.06 * 2) = 128. 0.1x + 0.12y = 128. Multiply by 100: 10x + 12y = 12800. Substitute x = 1200 - y: 10(1200-y) + 12y = 12800 => 12000 - 10y + 12y = 12800 => 2y = 800 => y = 400. Then x = 800. Ratio x:y = 800:400 = 2:1.

Multiple choice

The difference between S.I. and C.I. (compounded annually) on a sum of 64000 for 2 years is 1000. What is the rate of interest per annum?
  1. $25$%
  2. $\displaystyle16\frac{2}{3}\%$
  3. $\displaystyle13\frac{1}{3}\%$
  4. $\displaystyle12\frac{1}{2}\%$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For 2 years, the difference between CI and SI is P * (r/100)^2. Here, 1000 = 64000 * (r/100)^2. 1000/64000 = (r/100)^2, so 1/64 = (r/100)^2. Taking square roots, 1/8 = r/100. r = 100/8 = 12.5%.