Working together, Tim and Tom can type 15 pages in one hour. If they would be able to type 18 pages in one hour if Tom increases his typing speed by 60%, what is the ratio of Tom's normal typing speed to that of Tim?  Choose the correct choice from the following options:
A) 1 / 2  B) 1 / 3  C) 1 / 4  D) 1 / 5  E) 1 / 6

Rationale: "lets say tim types x pages an hour and tom types y pages an hour . we know that x + y = 15 tom increase speed by 60 % means he will type 1.6 y pages an hour . so we get x + 1.6 y = 18 we need to know the ratio of tom ' s speed to tim ' s speed . this is going to be proportional to the number of pages each can type in an hour , hence ( y / x ) . subtracting both : 0.6 y = 3 so y = 5 . . . so x = 10 ( y / x ) = 5 / 10 = 1 / 2 answer is ( a )"
Answer: A