NECO 2004 Mathematics · Question 13

A sales boy gave a change of N75.00 to a buyer instead of N80.00, calculate his percentage error, correct to one decimal place?

Options

A.6.00%
B.6.20%
C.6.30%
D.6.60%
E.6.70%

Answer: C. 6.30%

Explanation written with AI and checked against the answer key

Analyze the question: The correct change was N80.00, but the sales boy gave N75.00. We need the percentage error. Concept: Percentage error = (error ÷ correct value) × 100% Error = |correct value − value given| Solution: Error = 80 − 75 = N5.00 Percentage error = (5 ÷ 80) × 100% = 0.0625 × 100% = 6.25% Rounding to one decimal place: 6.25% rounds to 6.3% (rounding the 5 up). This matches option C, 6. Note: If you had divided by the wrong value (75), you would get 5/75 × 100 = 6.67%, which is option E. That is a trap. Always divide by the correct (true) value, which is N80.00 here. Tip: In percentage error questions, remember: error over true value, times 100. Also, when you get a value like 6.25 and must round to 1 decimal place, the digit 5 rounds up, giving 6.3.

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