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Question

I have no clue what this question is asking whatsoever. If you have gone through the princeton review practice tests, maybe you can shed some light?

If 4 d x d 12, is the tens digit of x! prime?

(1) x is even
(2) x! has exactly 3 distinct prime factors

richardj · Answer

Could you be slightly clearer on the format of the expression please ?

Are there any * or ^ symbols ?

trulyblessed · Answer

Richard, that is exactly what I would like to know. I typed it exactly as it appeared in the question. :roll:

richardj · Answer

I think there is a typo in the question and d should be < so,

f 4 < x < 12, is the tens digit of x! prime?

(1) x is even
(2) x! has exactly 3 distinct prime factors

 

Then (1) means x=6, 8, 10
x! = 720, 40320, 3628800
So tens digit x! = 2, 2, 0 (prime, prime, not-prime)
Not sufficient

Then (2)
the first four prime factors are 2,3,5,7
We must have first three, but not fourth.
So x=5 or x=6
x! = 120, 720 (prime, prime)
So sufficient assuming integers

So answer is B assuming integer x.

If not assuming integer X, answer is C, as we would have x=6, x!=720

macca · Answer

yes, I think richard got to be right. 

i also did a mock test from PR and got the same question. 
It must be a typo

trulyblessed · Answer

Dang you're good, Richard. B it is!

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