Hard Math Questions

[HW]

Hello,

I'm studying from the OG 10th edition. I am having a tough time on the hard math questions(mostly on the number properties ones). I need a 600-620 on the test. Are these types of questions in the 700+ level or not? Should I postpone the test(date set right now is April 28th) to get a better grasp of these number properties or should you only try to learn the hard questions if aiming for a 700+?

Thanks.

[Stacey Koprince]

Hi, HW - it's a little difficult for me to respond precisely to your query because I can't tell what you mean by "hard." The book doesn't tell you the difficulty levels of the questions - it just says that, generally, the later questions in a chapter are harder. But it's not a hard and fast rule, and I don't know at what point in the mix they are "too hard" for you.

Generally, yes, if you're going for a 600-620, you don't need to worry about the very hardest questions in there. (At least, you don't need to worry about getting them right - you'll still see some, but the computer will expect you to get them wrong, and that is what you want to do. Promptly. So that you don't waste time on questions you can't do and then cost yourself points on later questions that you can do but don't have time to get to.)

[HW]

Thanks for the reply.

There is a grid(that I found on this website) that classifies questions as easy,medium, and hard for the 10th edition. The questions that I have no clue about are the hard number property ones.

To give you an example from the 10th edition, Which of the following is the least positive integer that is divisiblle by 2,3,4,5,6,7,8, and 9? Whenever I encounter questions such as these I'm always thinking that how am I supposed to know and how is this relevant to anything in life. Is there any source that can help you with questions such as these or should I not worry since my goal is just 600-620?

[Stacey Koprince]

Oh, right - I forgot about that grid. That's not from the OG though - I think someone just assessed it and made best guesses.

For number properties, I would try to learn that stuff as thoroughly as you can just b/c that topic shows up all the time. The last time I took the test 12 of my 37 math questions were number properties - or about 1/3 of all questions.

For the example you give:
Which of the following is the least positive integer that is divisible by 2,3,4,5,6,7,8, and 9?

You basically want to break these down to prime and figure out the minimum you need for each one.

2: need a 2
3: need a 3
4: need two 2's (and already have one, so only need one more 2)
5: need a 5
6: need a 2 and a 3 (and we already have these, so can ignore)
7: need a 7
8: need three 2's (and already have two, so only need one more 2)
9: need two 3's (and already have one, so only need one more 3)

so that's:
2*3*2*5*7*2*3 = (2*2*5*2)*(3*7*3) = 40*63 (and then you might be able to just look at the answer choices rather than continuing to multiply this out - but you didn't provide the answers, so have to keep multiplying) = 2520.

[Stacey Koprince]

p.s.

And as to how this is relevant to anything in life? There I can't help you...

[rajesh_ctm]

Whenever I encounter questions such as these I'm always thinking that how am I supposed to know and how is this relevant to anything in life.

Though you need to be comfortable working with numbers if you are aspiring to be a good manager, I agree these questions are not relevant to your life. What is relevant to things in your life cannot be directly tested. You might learn all the theoretical stuff and ace the exams, but still fail to apply them in your real life.

In fact many things you have learnt since childhood are not relevant to your life. But learning those has improved your intellect. What is relevant to your life is your learnability rather than the things learnt. GMAT probably tries to test the learnability rather than the learnt.

[beatthegmat]

Whenever I encounter questions such as these I'm always thinking that how am I supposed to know and how is this relevant to anything in life.

Though you need to be comfortable working with numbers if you are aspiring to be a good manager, I agree these questions are not relevant to your life. What is relevant to things in your life cannot be directly tested. You might learn all the theoretical stuff and ace the exams, but still fail to apply them in your real life.

In fact many things you have learnt since childhood are not relevant to your life. But learning those has improved your intellect. What is relevant to your life is your learnability rather than the things learnt. GMAT probably tries to test the learnability rather than the learnt.

I agree that these kinds of questions may not be relevant to life--but they are certainly relevant to business school. I've heard that some schools have a reputation as being heavily quantitative, and brushing up on your math via GMAT is one step towards preparing yourself for the curriculum at b-school.

[HW]

Stuff like percentages/ratios/etc can be relevant to business/business schools. In fact, I'm glad they're tested on the GMAt because it gave me the opportunity to brush up on these topics. I was talking more about prime factorization/geometry...stuff like that. However, as Rajesh mentioned, it may be more of a test on how to take a test than anything.

What really surprised me was the fact that the 10th edition really does not explain concepts like prime factorization, both in the intro and the answer explanations. In fact, I learned more about it here than in the book.

In any case, thanks for your help Stacey.