JAMB 2020 Mathematics · Question 15

Find the simple interest rate percent annum at which N1000 accumulates to N1240 in 3 years.

Options

A.6%
B.8%
C.10%
D.12%

Answer: B. 8%

Explanation written with AI and checked against the answer key

1. Analyze the question

We are given:

Principal ( $P$ ) = N1000
Amount ( $A$ ) = N1240
Time ( $T$ ) = 3 years
We need to find the rate ( $R$ ) in percent per annum.

2. Explain the concept

Simple interest ( $I$ ) is calculated using the formula:

I = \frac{P \times R \times T}{100}

First, we must find the interest earned. The interest is the difference between the final amount and the principal:

I = A - P

Once we have $I$ , we can rearrange the simple interest formula to solve for $R$ :

R = \frac{I \times 100}{P \times T}

3. Show the solution

Step 1: Calculate the interest ( $I$ )

I = 1240 - 1000

I = 240

Step 2: Substitute the values into the rate formula

R = \frac{240 \times 100}{1000 \times 3}

Step 3: Simplify the calculation

R = \frac{24000}{3000}

R = \frac{24}{3}

R = 8\%

4. Identify the answer

Comparing our result to the given options: A. 6% B. 8% C. 10% D. 12%

The calculated rate is 8%, which corresponds to option B.

5. Tip

When dealing with simple interest questions in JAMB, always remember the acronym PRT. If you are asked for the rate, just remember: "Interest times 100, divided by the product of Principal and Time." Don't forget to subtract the Principal from the Amount first to get the Interest—many students mistakenly use the Amount ( $1240) in the interest formula instead of the Interest ($ 240)!

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