Question

The mean of 40 numbers was found to be 38. Later on, it was detected that a number 56 was misread as 36 . Find the correct mean of the ( data ) given no's

Answer 1

let S be the sum of 40 numbers.

S/40=38 which is calculated mean.
∴S=40 x 38=1520
But one of number misread as 36 instead of 56.∴Obtained sum S is 56-36=20 less than the actual sum.
∴The actual sum,S=1520+20=1540

∴Correct mean=S/40=1540/40=38.5