help with stupid GRE math question

[Special K]

This is a question I got off of the GRE powerprep program off of ETS's website. It looks ridiculously simple, but keep in mind you can't use a calculator and the test is 28 questions, 45 minutes, which means you must use shortcuts whenever possible. It's a quantitative comparison problem, just name which of these two quantities is greater:

100210 X 90021 OR 100021 X 90210

Again, the answer is obvious, but short of multiplying the numbers out by hand, which would take way too long for this timed test, I'm not seeing the shortcut to getting the answer. The program does not give explanations for the answers either. Could anyone here tell me the quick way to compare them?

thanks

 

[dighn]

the difference between the 2 versions of the numbers is 189 edit: what i mean is it's really

(100021+189)*90021 OR 100021*(90021+189)

189 * 90021 is smaller than 100021 * 189

 

[deftron]

Round.

 

[BigJ]

I guessed and said that the right one is greater. The reasons why I said this was because your multiplying a bigger number (100021) ~190 times instead of the smaller number (90021) which gives you a greater answer. By that I mean that 100021 * 190 is greater then 90021 * 190.

 

[Special K]

Originally posted by: dighn
the difference between the 2 versions of the numbers is 189 edit: what i mean is it's really

(100021+189)*90021 OR 100021*(90021+189)

189 * 90021 is smaller than 100021 * 189

That makes sense.

thanks