Question 52

The average age of a number of persons in a group was calculated as 35 years, which was 2.5 years more than the correct average as there was an error in recording the age of two persons as 38.5 years and 40 years instead of 29 years and 22 years respectively. The number of persons in the group was:

Solution

Let the number of persons be x.

Wrong average = 35

Total age for wrong average = 35x

Correct average = 35 - 2.5 = 32.5

Total age for correct average = 32.5x

Correct age of two persons = 29 + 22 = 51

Wrong age of two persons = 38.5 + 40 = 78.5

Difference = 78.5- 51

35x - 32.5x = 27.5

x = 27.5/2.5 = 11

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