Nikhil30
If there are 1/3 as many science majors as there are history majors,
i alwasy gets confused with this H=S/3.
Yes, these kinds of sentences are confusing. If we say "there are three times as many apples as bananas", that means "the number of apples is three times the number of bananas". It's confusing, because at first it sounds like we're multiplying the apples by 3, but we're not. This sentence means A = 3B (where A is the number of apples, B the number of bananas).
The same is true when you have a fraction in a sentence like this. If we say "there are 1/3 as many science majors as history majors", it might appear we should multiply science majors by 1/3, but that's not what this sentence means. It means "the number of science majors is 1/3 the number of history majors", and so it means, algebraically, S = (1/3)*H, or S = H/3.
These kinds of sentences show up all the time in GMAT math, so it's very important to know what they mean. If you find them confusing (which is normal!) I'd suggest you take a minute or two each day just to practice translating two or three sentences like this into algebra. It shouldn't take long before you're translating sentences like this correctly every time.