How many distinct prime divisors does a positive integer \(n\) have?

This topic has expert replies
Legendary Member
Posts: 2276
Joined: Sat Oct 14, 2017 6:10 am
Followed by:3 members

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

How many distinct prime divisors does a positive integer \(n\) have?

(1) \(2n\) has one distinct prime divisor.

(2) \(3n\) has one distinct prime divisor.

Answer: C

Source: GMAT Club Tests

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2621
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

If n is a positive integer, 2n is clearly divisible by 2. If, as Statement 1 says, 2n has only one prime divisor, that prime divisor must be 2. But then n can be 1, 2, 2^2, 2^3 or any other power of 2. Since it is possible n = 1, it is possible n has no prime divisors, and if n is any other power of 2, then n has one prime divisor.

Similarly Statement 2 means n is 1, 3, 3^2, 3^3 or any other power of 3. So n might have no prime divisors or one prime divisor.

Combining the Statements, the only possibility is that n = 1, so the answer is C.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com