Pcat math and chemistry question

[UT8305]

I need some help, I hope this doesn't sound stupid to anybody who doesn't have my problem. I know the material for gen chem, however when it comes to calculations, it very difficult for me to finish the problem since many questions require multi step multiplying and dividing like the gas laws, V2 = V2(P1/P2)(T2/T1), espcially when they give you big numbers and also things that you have to convert before you can use the actual equation), I find myself working more on getting through the mechanics then applying the concept to answer the question. This is really annoying to me because althroughout high school and college my chemistry classes required us to use calculators and we never not allowed to use one, and that goes for all colleges everywhere, how do they expect us to carry out calulations that we are use to doing simply on calc's manually all of the sudden, it changes the dynamics, I can understand the question and the concept they intend for the exam taker to apply, but i can't get through the math and my time and score suffer because of it, I know the little tricks but when ur divideding something like V2 = (4L)(320 torr/ 760 torr)(273K/588K), like in the equation i provided above (by the way this is not the only thing i have to do in this question, find MM) is there any way to get around the math?, becuase i'm not too good at calculating numbers in my head without writing it down first, and that takes forever on the test and is clearly not a good strategy.

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[omnione]

Generally, the numbers you need to input are easier numbers. If not, then you need to estimate.

For your problem, it'll be a little under 1 L:

4 * ~1/2 * ~1/2 = under 1 L

Both fractions are a little smaller than 1/2 but not quite 1/3 for either. If you want to get closer, I'd estimate that the answer is about 0.8.

Actual answer is 0.782 L, so I wasn't off by too much.