Manhattan Prep GMAT Forum

If Company M ordered a total of 50 computers and printers and Company N ordered a total of 60 computers and printers, how many printers did company M order?

(1) Company M and Company N ordered the same number of computers

(2) Company N ordered 10 more printers than Company M.

OA is E.

Here is my solution (initially chose C, because I did not solve the equations). Is there another way of approaching this problem? Thanks.

Let X=computers of M, Y=printers of M, Z=computers of N, T=printers of N

Looking for T

Facts: X+Y=50 ; Z+T=60

(1) X=Z ; This means that X+Y=50, Z+T=60. Could subtract equations and get that T-Y=10. INSUFFICIENT (know the relative difference, but not the exact #)

(2) Basically, this is the same equation as in (1) -- T-Y=10. No extra relationships so that we can calculate T or Y. INSUFFICIENT.

(1)^(2) INSUFFICIENT, since they are the same equations

kourakis Wrote:Is there another way of approaching this problem? Thanks.

as in the case of many algebraic problems, you can also pick numbers. since it's a data sufficiency problem, the goal is to try to get multiple numbers that satisfy the statements, thereby proving them insufficient. (if you can only find one number or set of numbers that satisfies the given constraints, then you pick "sufficient".)

here are some choices of numbers:

* both companies order 40 computer; M orders 10 printers; N orders 20 printers

* both companies order 1 computer; M orders 49 printers; N orders 59 printers

these choices satisfy both statements, so both statements together are still insufficient -- therefore (e)

Hi -

For these kinds of DS questions -- is it better to use algebraic or plug in - Just wondering how high level test takers do this kind of question ?

-- I used algebra but i got confused b/w C and E

-- using algebra, easily 2.30 seconds are eaten up by the time i get between C and E and i normally panic and just guess and move on (My guess turns out to wrong most of the time)


Please let me know your thoughts

Good question. Strategy choice is a skill, and accumulating experience (and reflecting on what worked and what didn't) is important here. When the numbers are pretty small, as in this case, then I would tend towards testing cases. I can think pretty quickly for the individual statements "oh, it could be ... or it could be ...". So I wouldn't use equations for this problem, and, in fact, I rarely use equations when equations are not provided in the problem.

Noting that each statement is really just giving you the same information is quite a useful insight. This means that the answer can only be D or E.