Tricky Ways to Indicate Number Properties

[rdjaye]

In some of the OG questions, there can be tricky language to indicate number properties.

Two examples:
1. "n has exactly two factors" --> MEANS n is a prime number
2. "x/n is an integer" --> MEANS n is a factor of x

What other tricky language should we look out for to indicate if something is a prime, multiple, factor, etc.? I'm sure this will help grasp quant questions within the 2 minutes or less timeframe. Thank you!

[RonPurewal]

In some of the OG questions, there can be tricky language to indicate number properties.

Two examples:
1. "n has exactly two factors" --> MEANS n is a prime number
2. "x/n is an integer" --> MEANS n is a factor of x

What other tricky language should we look out for to indicate if something is a prime, multiple, factor, etc.? I'm sure this will help grasp quant questions within the 2 minutes or less timeframe. Thank you!

There's not going to be any sort of ready-made list for this sort of thing.

The best prescription is this: Just play around with the statements that you're given. If they're hiding any sort of fact about number properties, that fact is going to emerge pretty quickly.

E.g.,
With your #1, let's just look at how many factors the first few integers have.
1 has 1 factor.
2 has 2 factors.
3 has 2 factors.
4 has more than 2 factors (1, 2, 4).
5 has 2 factors.
6 has more than 2 factors. (After I find a third one, I don't care, because I only care about numbers with 2 factors.)
7 has 2 factors.
Etc.
You'll notice pretty quickly that the numbers with two factors are 2, 3, 5, 7, etc. Oh hey, those are prime numbers.

With your #2, same thing. Just list out a few x & n so that x/n is an integer, and it'll be pretty easy to see what the deal is.

(If you had to anticipate the "tricky language" ahead of time, I wouldn't do very well on this test.)