Problem Solving

serendipiteez wrote:Can it be generally said that in Problem Solving questions on the GMAT, it is better to work from E to A instead of A to E because the testmaker is trying to make you work through the answer in order.

Those with experience, hoping you can shed light on whether this is a good "strategy".

It depends on the question type and/or your approach.

For questions where you find the solution and then look for the correct response among the answer choices, it makes no difference which order you use. For example:
If shirts cost $3 each, what is the cost of 10 shirts.
(A) $13
(B) $20
(C) $30
etc.
Here, if you first solve the question (to get $30), then it doesn't matter which order you check the answer choices.


However, if you have a question where you must check every answer choice, then I think it's best to check from E to A. For example:
Which of the following equations shares has the same solution as the equation 2x = 6?
(A) 5x + 1 = 14
(B) 3 - 6x = 12 + 3x
(C) 3(x - 4) = 1 - 2(2x + 1)
etc
Here, once we solve the equation 2x = 6 to get x = 3, we must then begin solving (or testing) the equations among the answer choices to see which one has x = 3 as its solution.
In these instances, it has been my experience that the test-makers place the correct answer near the bottom of the answer choices (typically D or E). So, I check the answer choices from E to A.


Finally, for questions that you are trying to solve solely by plugging in values, it's often useful to begin with answer choice C and then use the results to help direct the next value you check. For example:
Bob is 7 years younger than Al. If the sum of their ages is 65, how old is Bob?
(A) 23
(B) 29
(C) 36
(D) 37
(E) 39
Many students will find an algebraic approach to this question and that's great. But sometimes it's actually faster to simply plug in the answers (especially if you don't see the algebraic approach).

When you plug in values, it's best to start with the middle value.

So, let's try C and see if it satisfies the given information.
If Bob is 36, then Al is 43, which means the sum of their ages is 79
We need the sum to be 65, so we can eliminate C.
IMPORTANT: Since we need the sum to be 65, we need the men to be younger.
In other words, Bob must be younger than 36.
So, we can eliminate D and E.

At this point, we have two answer choices remaining (A and B).
Which one should we test next?
It doesn't matter.
For example, if we test A first and it works, then A is correct (DONE!)
If we test A first and it doesn't work, then B must be correct (DONE!)

I hope that helps.

Cheers,
Brent