The mean of 50 observations was 160. It was detected on rechecking that the value 175 was wrongly copied as 75 for the computation of the mean. Find the correct mean.

x=(160*50+100)/50=162

Randy had grades of 96, 87, 99, 55, and 85 what grade does he need to have an average of 85?

Assuming he will take one more grade and all scores have the same weight 

(96+87+99+55+85+x)/6=85 

which leads to x=88

Tony has the following data:


14, X, 19, 9, 8


If the mean is 14, what is the value of X?


Solution:

The mean of all five numbers is 14 even though we don't know X.
So we can write the following: