Question 62

The average of 30 numbers is 36. If Z is subtracted from each of these 30 numbers, then the average becomes 28. What is the value of Z?

Solution

The average of 30 numbers is 36.

Total of 30 numbers = $$36\times30$$ = 1080 Eq.(i)

If Z is subtracted from each of these 30 numbers.

So the required subtraction from total is '30Z'. Eq.(ii)

New average = 28

New total of 30 numbers = $$28\times30$$ = 840 Eq.(iii)

Eq.(i)-Eq.(ii) = Eq.(iii)

1080-30Z = 840

30Z = 1080-840

30Z = 240

Z = 8

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