calculus
posted by :) .
Find two positive numbers whose product is 100 and whose sum is a minimum.

S=a+b
but a= 100/b
S=100/b + b
dS/db=0=100/b^2 +1
solve for b, then go back and solve for a. 
i hope i got it right. The two numbers are 10 and 10?

Exactly right. It's just the same as finding a rectangle of maximum area for a given perimeter. It's always a square.

thanks guys!