Simple & Compound Interest

Ladakh Police Sub-Inspector · Mathematics · 49 practice questions with answers and explanations: 21 Easy, 27 Medium, 1 Hard.

Sample questions

Sample Easy question 1

A sum doubles itself in 10 years at simple interest. Find the rate of interest.

  1. 9%
  2. 10%
  3. 12%
  4. 8%
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Answer: B. SI equals the principal in 10 years, so rate = 100/10 = 10%.

Sample Easy question 2

Find the simple interest on Rs. 1500 for 2 years at 5% per annum.

  1. 150
  2. 160
  3. 140
  4. 120
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Answer: A. SI = (1500 × 5 × 2)/100 = 150.

Sample Easy question 3

Find the simple interest on Rs. 3000 at 8% per annum for 5 years.

  1. 1200
  2. 1000
  3. 1100
  4. 1300
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Answer: A. SI = (3000 × 8 × 5)/100 = 1200.

Sample Medium question 4

The difference between the compound interest (compounded annually) and the simple interest on a certain sum for 2 years at 10% per annum is Rs. 200. Find the sum.

  1. Rs. 21000
  2. Rs. 40000
  3. Rs. 20000
  4. Rs. 10000
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Answer: C. For 2 years, CI − SI = P × (r/100)². So P = 200 × (100/10)² = Rs. 20000.

Sample Medium question 5

The difference between the compound interest (compounded annually) and the simple interest on a certain sum for 2 years at 15% per annum is Rs. 45. Find the sum.

  1. Rs. 3000
  2. Rs. 4000
  3. Rs. 2000
  4. Rs. 1000
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Answer: C. For 2 years, CI − SI = P × (r/100)². So P = 45 × (100/15)² = Rs. 2000.

Sample Medium question 6

Find the compound interest on Rs. 10,000 for 2 years at 10% per annum.

  1. 2200
  2. 2000
  3. 2100
  4. 2050
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Answer: C. CI = 10000 × (1.1² - 1) = 10000 × 0.21 = 2100.

Sample Hard question 7

Find the compound interest on Rs. 10,000 for 1.5 years at 10% per annum, compounded half-yearly.

  1. 1600
  2. 1576.25
  3. 1500
  4. 1550
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Answer: B. With 5% per half-year over 3 periods, amount = 10000 × 1.05³ ≈ 11576.25, so CI ≈ 1576.25.

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