The money John has is just enough to buy him either 100 apples and 150

We can just test the answer choices. It's worth noting that I believe that if this question were written by GMAC, the answer choices would probably be in either ascending (1:3, 3:5, 2:3, 5:6, 1:1) or descending order. I'll use the answer choices in that order to show the technique.
1:3
3:5
2:3
5:6
1:1

When Plugging In The Answers (PITA), I usually like to start with B and D (the second and fourth options of the five). 1:1 looks really easy to work with, so I'd probably do that one quickly to start, but just to show how to use PITA to test at MOST two options and still get the right answer.

Let's start with the second option in the list above, 3:5.
100 apples costs $3. 150 oranges costs $5. That's a total of $8, so that's what John has in his pocket to spend.
50 apples costs $1.50. 225 oranges costs $7.50. That's a total of $9. Sorry, John, you don't have enough anymore!

Let's try the fourth option in the list above: 5:6.
100 apples costs $5. 150 oranges costs $6. That's a total of $11, so that's what John has in his pocket to spend.
50 apples costs $2.50. 225 oranges costs $9. That's a total of $11.50. Sorry, John, you're getting closer, but you still don't have enough.

The first thing we tested was too expensive by $1 (out of $8). The second thing we tested was too expensive by $0.50 (out of $11). Are we getting farther away? No, so 1:3 is out. Are we getting closer, but need to keep going? Yep, so 1:1 is correct. That's A in the original question.

Answer choice A.


ThatDudeKnowsPITA