Simple & Compound Interest Quiz: Quantitative Aptitude Practice

Spoilers! These are the Starter quiz’s answers. Easy, Medium, Hard and Mixed rounds show their own answers when you finish.

1. What is the simple interest on Rs 8,000 at 7.5% per annum for 3 years?

   • Rs 1,800
   • Rs 1,600
   • Rs 2,400
   • Rs 1,920

   Answer: Rs 1,800. SI = 8,000 × 7.5 × 3/100 = Rs 1,800.

2. A sum of money doubles itself in 8 years at simple interest. What is the rate of interest per annum?

   • 10%
   • 8%
   • 12%
   • 12.5%

   Answer: 12.5%. Doubling means SI = P, so R × T = 100 and R = 100/8 = 12.5%.

3. What is the compound interest on Rs 10,000 at 10% per annum for 2 years, compounded annually?

   • Rs 2,000
   • Rs 2,100
   • Rs 2,200
   • Rs 2,010

   Answer: Rs 2,100. Amount = 10,000 × 1.1 × 1.1 = 12,100, so CI = Rs 2,100 (21% over two years).

4. What is the difference between compound interest and simple interest on Rs 15,000 at 8% per annum for 2 years?

   • Rs 120
   • Rs 96
   • Rs 48
   • Rs 108

   Answer: Rs 96. For 2 years, CI - SI = P(R/100)² = 15,000 × 0.0064 = Rs 96.

5. A sum amounts to Rs 9,440 in 3 years and Rs 10,400 in 5 years at simple interest. What is the sum?

   • Rs 7,600
   • Rs 8,400
   • Rs 7,800
   • Rs 8,000

   Answer: Rs 8,000. Two years' interest = 10,400 - 9,440 = 960, so Rs 480 a year. Sum = 9,440 - 3 × 480 = Rs 8,000.

6. What is the compound interest on Rs 16,000 at 10% per annum for 1 year, compounded half-yearly?

   • Rs 1,640
   • Rs 1,600
   • Rs 1,680
   • Rs 1,620

   Answer: Rs 1,640. Half-yearly means 5% for 2 periods: 16,000 × 1.05 × 1.05 = 17,640, so CI = Rs 1,640.

7. A sum becomes 4 times itself in 6 years at compound interest. In how many years will it become 16 times itself?

   • 18 years
   • 24 years
   • 12 years
   • 15 years

   Answer: 12 years. 16 = 4², so it takes 2 × 6 = 12 years. At CI the multiples multiply.

8. What amount will Rs 12,000 become in 3 years at 20% per annum compound interest (compounded annually)?

   • Rs 19,200
   • Rs 20,160
   • Rs 21,736
   • Rs 20,736

   Answer: Rs 20,736. 12,000 × 1.2³ = 12,000 × 1.728 = Rs 20,736.

9. What is the difference between compound interest and simple interest on Rs 8,000 at 5% per annum for 3 years?

   • Rs 61
   • Rs 60
   • Rs 62
   • Rs 65

   Answer: Rs 61. CI - SI for 3 years = P(R/100)²(3 + R/100) = 8,000 × 1/400 × 3.05 = Rs 61 (CI 1,261 - SI 1,200).

10. What is the effective annual rate of interest for 10% per annum compounded half-yearly?

    • 10%
    • 10.5%
    • 10.25%
    • 10.125%

    Answer: 10.25%. (1.05)² = 1.1025, so the effective yearly rate is 10.25%.