Manager
Joined: 06 Mar 2015
Status:Owner, Reason Test Prep
Affiliations: Reason Test Prep
Posts: 51
GMAT 1: 780 Q50 V47
GMAT 2: 790 Q50 V51 (Online)
GRE 1: Q170 V169
GRE 2: Q170 V169
Re: If the volume of a small container is 14,520 cubic millimeters, what i
[#permalink]
19 Jul 2021, 13:19
From a strategic perspective there are a couple important things that one can do on this question. In my experience, many people fall for the trap answer (E) because they obviously only convert units once instead of 3 times. This is a pretty easy question if you understand that you need to convert for each side, but that understanding is not obvious to people who just don't already know that ahead of time. So how can such a person avoid falling into a trap on questions like these?
Well first of all, one should be very suspicious of Choice E here. I wouldn't say it's impossible that E could be right, but I'd certainly be very suspicious of it and quadruple check it. Ok, but again, how can you check it if you don't just know in advance that you have to convert units for each side?
Well number picking helps here. One could just create sample side lengths that would lead to a volume of 14,520mm. To make it easy, we could imagine that the container is 1mm by 1mm by 14,520mm. Certainly those could be the side lengths, right? Well if you think about it, 1mm is .1cm. So that would be true of both of those sides, and just like that you'd start to see that maybe you need to convert multiple times. And then the side of 14,520mm would be 1,452cm. If you just do the math on that, it's .1cm x .1cm x 1452cm = 14.52cm, or Choice C.
So sure, it helps to know in advance that one needs to convert for each side, but knowing that Choice E is a trap and then just creating an actual example with side lengths to test it is a way to get to the right answer without that prior knowledge. And the GMAT is full of traps like this, so being able to sniff out the traps and having some creative/strategic ways of getting to answers even when one isn't totally sure about the underlying Math knowledge is important!