Here's the full question:

For any positive integer n, the length n is defined as the number of prime factors whose product is n. For example, the length of 75 is 3, since 75= 3 X 5 X 5. How many two-digit positive integers have length 6?

A) None
B) One
C) Two
D) Three
E) Four


Let's first find the smallest value with length 6.
This is the case when each prime factor is 2.
We get 2x2x2x2x2x2 = 64. This is a 2-digit positive integer. PERFECT

To find the next largest number with length 6, we'll replace one 2 with a 3
We get 3x2x2x2x2x2 = 96. This is a 2-digit positive integer. PERFECT

To find the third largest number with length 6, we'll replace another 2 with a 3
We get 3x3x2x2x2x2 = 144. This is a 3-digit positive integer. NO GOOD

So there are only two, two-digit positive integers with length 6.

Answer = C

Cheers,
Brent