What is the sixth number?

Question

five of six numbers have a sum of 25. The average of all six numbers is 6.

 

Answer 1

Suppose the 6 numbers are A, B, C, D, E and F.

 

"Five of six numbers have a sum of 25. "       means    A+B+C+D+E = 25           [omit F]

 

"The average of all six numbers is 6"   [note: Average=Sum/Count]  means   (A+B+C+D+E+F)/6 = 6

 

From the second equation, (A+B+C+D+E+F)=36    [multiply both sides by 6]

 

Now, we have:

       (A+B+C+D+E+F) = 36

  and

       (A+B+C+D+E)  = 25

 

So, what value does F have?

Answer 2

If the average of all 6 is 6 then the sum of all 6 is 36.

If the sum of 5 numbers is 25 then then 6th number of 11.