this question is ridiculously easy with the right method and midset: plugging in and elimination.srcc25anu wrote:
x/y = 2/5 is just a ratio between x and y. x and y CAN be 2 and 5, or 4 and 10, or 6 and 15: any of these pairs can be reduced to 2/5. (try it!: If x=4 and y=10, then x/y = 4/10 = 2/5, so 4 and 10 are valid plug ins).
With this in mind, I is not MUST be true: x+y CAN equal 7 (for x=2 and y=5), but it doesn't have to equal 7: if x=4 and y=10, then x+y is equal to 14, not 7.
Once you realize that I is not a MUST, you can eliminate any answer choice that claims otherwise: A, B, C and E are out, leaving D as the only viable answer, without looking at II and III.
Two main takeaways:
1) In Must be true questions, plug in and eliminate: don't try to fine the answer that must be true, but rather try to find a counter example that shows that the answer is NOT True, and thus needs to be eliminated.
2) In "statements" questions, it pays to eliminate one statement at a time. Once you have made a decision regarding, see which answer choices can be eliminated first before moving directly to II. It is sometimes possible to skip a statment or two entirely just by POE.
