If 1/a + 1/b = 1/c and ab=c, what is the average of a and b?

If we solve the left side of the given equation,

1/a + 1/b = 1/c

we get an answer of,

b+a / ab = 1/c

Since ab = c, we can conclude that b + a is 1. The average of these two numbers is equal to there sum divided by 2. The answer is therefore equal to 0.5.