JAMB 2015 Mathematics · Question 22

If duty is levied at 25%, find the duty to be added to a bill of N80.

Options

A.N100
B.N20
C.N80
D.N150

Answer: B. N20

Explanation written with AI and checked against the answer key

Analyze the question: A duty of 25% is charged on a bill of N80. We need the amount of duty, which is the amount added to the bill. Concept: Duty = (rate/100) × amount Solution: Duty = 25% of N80 Duty = (25/100) × 80 Duty = 0.25 × 80 Duty = N20 Check: the new total would be N80 + N20 = N100. That is why N100 (option A) is a tempting distractor, but it is the total bill, not the duty. The question asks only for the duty to be added. Answer: The duty is N20, which is option B. Tip: 25% is the same as one quarter, so you can quickly divide by 4: 80 ÷ 4 = 20. Always check whether the question asks for the amount of the duty (or the percentage) or for the new total.

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