Each of the digits 7, 5, 8, 9, and 4 is used only once

[BrandenF768]

[redacted]

[RonPurewal]

hi,
per the forum rules, please cite the original source of this problem. thank you.

[BrandenF768]

Source: GMAT Prep Exam 3 from Exam Pack 1.

[RonPurewal]

we can't use any paid GMAC materials here. please familiarize yourself with the forum rules before posting -- thanks.

[RonPurewal]

in terms of the problem that was posted here -- if it's a "how many" question and the answers are things like 2 and 3 and 4 and 5, then, it should be pretty obvious that the only possible way to solve the problem is to count/list all the possible ways.
the challenge will lie in organizing or narrowing the possibilities before you do that.

if it takes you 3.5 forevers to go through all the possibilities, then you probably aren't narrowing things down enough before you start the process -- in other words, you are probably wasting time considering examples that are irrelevant and that could be eliminated upfront by some quick method or another.