Question

The arithmetic mean of the square
of 5 distinct quantities is 45.
Later it was found that one quantity
yous wrongly taken as 5 instead of 7.
Find the corrected arithmetic mean.
​

Answer 1

Answer:

Mean of 9 observation =45.

x

ˉ

=45

n=9

x

ˉ

=

n

∑x

∑x=

x

ˉ

n=45×9=405

Sum of all observation are 405.

Now an observation was wrongly taken as 42 for 24.

∴ 42−24=18 was mistakely added more.

∴ ∑x−18=387=∑y [the correct sum of all observation.]

∴

y

ˉ

=

n

∑y

=

9

387

=43

∴43 is the correct mean.