<PRE><B>Question 1129606</B>
The average set of n numbers is 23. When -35 is added to the set, the average is 21.
 How many numbers were in the original set? 
:
{{{(23n-35)/(n+1)}}} = 21
23n - 35 = 21(n+1)
23n - 35 = 21n + 21
23n - 21n = 21 + 35
2n = 56
n = 56/2
n = 28
:
:
Check this
23(28) - 35 = 609
609/29 = 21</PRE>