A  trader gave a change of # 540.00 instead of # 570.00 to a customer. Caculate the percentage error.

Analyze the question: The trader gave ₦540 when the correct change was ₦570. We need the percentage error.

Concept: Percentage error = (error ÷ true value) × 100%

The true (correct) value is ₦570, and the error is the difference between the correct and the given amount.

Solution:

Error = 570 − 540 = ₦30

Percentage error = (30 ÷ 570) × 100% = (1/19) × 100% = 100/19 %

Dividing: 100 ÷ 19 = 5 remainder 5, so

= 5 5/19 %

Check against the options:

• A. 5 5/19 % ✔
• B. 5 5/9 % (this would come from 30/540, which wrongly uses the given amount as the base)
• C and D do not match.

Tip: Percentage error is always measured against the true/correct value, not the wrong one. Here the correct change was ₦570, so divide by 570. Many students fall into the trap of dividing by 540, which gives option B.