Problema Solution

I have a list of 5 numbers whose mean is 12. If I remove one of the numbers, the mean becomes 13. What is the value of the number I removed?

Answer provided by our tutors

let 'x' represent the number that gets removed and 't' represent the total, or sum, of the other four numbers, then we know that:


a list of 5 numbers whose mean is 12:

(t+x)/5 = 12


If I remove one of the numbers, the mean becomes 13, so we remove 'x' and we can solve for 't':

t/4 = 13

t = 52


we revisit the first equation, substituting 't' with '52' and solving for 'x':

(52+x)/5 = 12

x = 8


the number that was removed is 8