Question

mean of 100 observation is found to be 40 . At the time of computation, 2 items were wrongly taken as 3 and 72 instead of 30 and 27. Find the correct mean

Answer 1

$\huge\boxed{\texttt{\fcolorbox{Red}{aqua}{Hey Mate!!!}}}$

Mean = Sum of number/ Total numbers
Sum of 100 numbers = 40 x 100
= 4000
So mistake is in the sum which reads 3 and 72 instead of 30 and 27
so the new sum of number is
$= 4000 - 3 - 72 + 30 + 27 \\ = 3982$

So the correct mean =
$= \frac{3982}{100} \\ = 93.82$
Hope it helps you

Answer 2

Number of observations=100

Mean=40

Sum of values of observations=40×100

=4000

30 and 27 noted instead of 3 and 72

Correct sum=4000−30−27+3+72

=3982

Correct mean=

100

3982

=39.82