GMAT Math

I agree you can do DS on average quicker than PS. Still, some DS questions genuinely take a long time to solve. That said, if you can solve DS questions in about 1m30 on average, and PS questions in about 2m20 on average, you're on good pace for the test.

As for time strategy:

If you have enough time to prep for the test, you should be able to develop an 'internal clock'; you should know when you are spending more than two minutes on a question. If you don't have much prep time, you should learn some benchmarks and verify your progress during the test. You certainly want to reserve enough time so that you don't need to guess at more than one or two questions at the end of your test- and preferabley none, of course. Guessing at several questions at the end of your test is a sure way to kill your score.

On one question, my general advice about time is this: after about 1m to 1m30, you should ask yourself: do I have a path to a solution. If you do, and it won't take an extraordinarily long time to complete, finish it: correct answers are worth a lot on the test. Even if the whole question will take you three minutes, finish it. But if, after 1m15 or so, you don't see a path to the answer, then it's time to think of fall-back strategies: choosing numbers, plugging in answer choices, estimating, etc, to eliminate wrong answer choices. You do not want to be guessing completely randomly, unless that's unavoidable- eliminate as many wrong answers as you can. Ideally, when you need to guess, you'll be guessing at least one-in-three, and preferably one-in-two. You can learn how to guess well on the GMAT, but it's certainly more helpful to learn how to do the math and verbal first- guessing is the last thing you should focus on.

The main point is, never be stubborn about a question. You'll see many GMAT questions that look easy- that look as if they test mathematics that you should know- but that are very difficult to solve on the spot, under test pressure. You need to be willing, after one minute, to cut your losses and move on- the time you save will help you later. Still, never give up on a question immediately: some questions are much easier than they appear at first. Always give some thought to each question you see- the ones that appear the most confusing at first are often the easiest to solve once you understand what is being asked. But if after a minute and a bit, if you can't see any path to an answer, then it's time to think of how to rule out wrong answers.

pepeprepa wrote:I am wondering, do you check your method? I mean, you have the method, you solve it and you have your answer which is one of the A B C D E possibilities, is it necessary to check that you did not make any error?

For example, after 40" you sure at 90% to have the right answer of a DS question, would you take the time till 1'30 to be sure at 99% of your answer or do you stop after 40" to save time?

If you are asking whether I check my answers, yes, always, and often twice, but that's because I know I can afford to spend the time to do that. Whether it's a good idea to check your answers really depends on your abilities:

-do you make many careless mistakes?
-if you spent more time on a question, would you notice a careless mistake and be able to correct it?
-how important is time to you on the test? Can you finish the test with time to spare?

Some test-takers, when doing practice questions, dismiss their careless mistakes too quickly- I think many people look back at some questions that they got wrong and say 'oh, that was just a stupid error, I added the powers when I should have multiplied them' and move on. If you make a careless mistake on a practice question, you'll probably make the same careless mistake on a real GMAT question unless you learn to avoid that mistake.

If you can work out when you make careless mistakes, you can often train yourself to avoid them. Often people make careless mistakes in similar situations- some will consistently make mistakes with exponent rules, others with negative signs, others will misread questions, etc. Suppose you often make mistakes when using exponent laws, and you see an exponents question on the test. What you want to do is to slow down and check your work while you are solving the question, not at the end of the question. If you do make a careless mistake early in your calculations, then complete the rest of the question, you'll have to redo the entire question if you only see the mistake at the end. It saves time in the long run to not make the mistake in the first place.

One of the great advantages of practicing with GMATPrep is that it helps you to determine whether time is an issue for you. If you can complete the test with time to spare, you can certainly afford to spend some time checking your answers during the test. If time is a major issue for you (and it is for most test-takers), but you are very careful with your work and rarely make careless mistakes, checking your work is likely to be counterproductive.

So whether you should check your work depends on how many mistakes you are likely to fix by checking your work, and how valuable extra time will be for you on the test- there's no universal advice I'd give to everyone about this.