gmatprep

[g.shankaran]

for any +ve integer n, the length of 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 integers have length 6?

1. none
2. 1
3. 2
4. 3
5. 4

[Calvin123]

for any +ve integer n, the length of 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 integers have length 6?

1. none
2. 1
3. 2
4. 3
5. 4

IMO 2. 1

because 2^6=64 if you try to replace any 2 from 3 it will be
2*2*2*2*2*3=106 which is 3 digit no.
so for 2 digit no it will be 64 only, which has 6 length.

[vinayreguri]

Ans 2. 2 numbers in total.

2*2*2*2*2*2=64
2*2*2*2*2*3=96

I see these questions in MGMAT forums also.

[Calvin123]

Ans 2. 2 numbers in total.

2*2*2*2*2*2=64
2*2*2*2*2*3=96

I see these questions in MGMAT forums also.

My bad.. ans must be 2, i did silly calculation mistake

[Geva@EconomistGMAT]

Ans 2. 2 numbers in total.

2*2*2*2*2*2=64
2*2*2*2*2*3=96

I see these questions in MGMAT forums also.

My bad.. ans must be 2, i did silly calculation mistake

Slow down, score more. It's always good to spend an extra 10 seconds taking another look at your logical path before committing to an answer - try to pick up on hidden assumptions that you're making (such as that fact that the prime factors don't need to all be the same, in the case above).