WAEC 2017 Mathematics · Question 19

If the simple interest on a certain amount of money saved in a bank for 5 years at 2 1/2 % annum is N500.00…

Question

If the simple interest on a certain amount of money saved in a bank for 5 years at 2 $\frac{1}{2}$ % annum is N500.00, calculate the total amount due after 6 years at the same rate

A.N2,500.00
B.N2,600.00
C.N4,500.00
D.N4,600.00

Answer: D. N4,600.00

Explanation written with AI and checked against the answer key

Step 1: Analyze the question We're told the simple interest for 5 years at 2½% per annum is N500. We need to find the principal, then the total amount (principal + interest) after 6 years. Step 2: Concept Simple Interest: I = PRT/100 Amount = Principal + Interest Step 3: Solution Find the principal: 500 = P × 2.5 × 5 / 100 500 = 12.5P / 100 500 = 0.125P P = 500 / 0.125 = N4,000 Interest for 6 years: I = 4000 × 2.5 × 6 / 100 = N600 Total amount after 6 years: A = 4000 + 600 = N4,600 Step 4: Answer The total amount due is N4,600.00, which is option D. Tip: Once you have the principal, you can also note that the interest is N100 per year (500 ÷ 5). So for 6 years it is N600, and you simply add it to the principal: 4000 + 600 = 4600. Always check whether the question asks for the interest or the total amount. Option A and B would be traps if you forgot to find the principal first!

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