stonecold wrote:

For how many positive integers is the number of factors equal to the number itself?

A) one

B) two

C) three

D) four

E) cannot be determined

Start TESTING values.

The factors of 1: {1}. 1 factor. WORKS!

The factors of 2: {1,2}, 2 factors. WORKS!

The factors of 3: {1,3}, 2 factors. Doesn't work

The factors of 4: {1,2,4}, 3 factors. Doesn't work

As we can see, if an integer n has n factors, then the factors of n must be: {1, 2, 3,....., n)

So, we can quickly see that the only positive integers that meet this criterion are 1 and 2

Answer:

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Brent Hanneson – Founder of gmatprepnow.com