1/x is smallest when x is the largest it can be, so it is 1/3
1/y is smallest when y is the largest it can be, so it is 1/5
The average of 1/3 is 1/5 can be found by adding them together and dividing by 2:
1/3 + 1/5 = 5/15 + 3/15 = 8/15
Divide it by 2:
4/15
The answer is C.
