If xy > 0, 1/x + 1/y = 15, and 1/xy = 5, then (x+y)/5 = ?  Select.
A) 1 / 25  B) 1 / 6  C) 3 / 5  D) 5  E) 6

Rationale: ( 1 / x + 1 / y ) = 15 canbe solved as { ( x + y ) / xy } = 5 . substituting for 1 / xy = 5 , we get x + y = 15 / 5 = = > ( x + y ) / 5 = 15 / ( 5 * 5 ) = 3 / 5 . c
Answer: C