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. 

It is b as the correct answer is 0.088, you are able to work these out on a calculator or without a calculator if you type in the exact sum that is given for harder questions like these!