Question

Difficulty: MediumFinancial Mathematics (Interest, Profit, Loss, and Depreciation)

A trader deposited 40,000\text{₦}40,000 in a microfinance bank offering compound interest at the rate of 10%10\% per annum, compounded annually. What is the total interest earned by the trader at the end of 22 years?

  1. A
    8,000\text{₦}8,000
  2. 8,400\text{₦}8,400Answer
  3. C
    40,400\text{₦}40,400
  4. D
    48,400\text{₦}48,400

Answer

The total interest earned by the trader at the end of 22 years is 8,400\text{₦}8,400.
Using the compound interest formula A=P(1+r)nA = P(1 + r)^n, the total accumulated amount after 2 years is 40,000×(1.1)2=48,40040,000 \times (1.1)^2 = \text{₦}48,400. Subtracting the original principal of 40,000\text{₦}40,000 gives the compound interest earned: 48,40040,000=8,40048,400 - 40,000 = \text{₦}8,400.

Step-by-Step Solution

1
Calculate the total accumulated amount (AA) using the compound interest formula A=P(1+R100)nA = P\left(1 + \frac{R}{100}\right)^n.
A=40,000(1+10100)2=40,000×(1.1)2=40,000×1.21=48,400A = 40,000\left(1 + \frac{10}{100}\right)^2 = 40,000 \times (1.1)^2 = 40,000 \times 1.21 = \text{₦}48,400.
The compound interest formula yields the total value of the investment after 2 years.
2
Subtract the initial principal (PP) from the total accumulated amount (AA) to find the compound interest (II).
I=AP=48,40040,000=8,400I = A - P = 48,400 - 40,000 = \text{₦}8,400.
Interest earned is the difference between total final amount and initial principal.

Key Concept

Calculation of compound interest vs total accumulated amount
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