Question
The average marks obtained by 20 students in a test is 74.
It was later found that 78 was wrongly recorded as 87 and 69 was wrongly written as 63. What is the revised average?Solution
ATQ,
Correct average
= {(20 × 74) – 87 + 78 – 63 + 69} / 20
= {1480 – 87 + 78 – 63 + 69} / 20
= 1480 – 87 = 1393 + 78 = 1471 – 63 = 1408 + 69 = 1477
Correct average = 1477 / 20 = 73.85
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