In a class of 30 students, the average mark on a test is 65. The teacher discovers that one student's mark of 84 was wrongly recorded as 48. After correcting the error, the new average is:
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Worked Solution
Step 1: The error under-counted by 84 − 48 = 36 marks.
Step 2: Spread over 30 students, the average rises by 36 ÷ 30 = 1.2.
Step 3: New average = 65 + 1.2 = 66.2.
Answer: 66.2
Correct answer: 66.2
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