Length based on prime factor

This topic has expert replies
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Sat May 16, 2009 5:09 am

Length based on prime factor

by bharatv » Sat May 16, 2009 11:13 pm
For any positive 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 positive integers have length 6?

a. none
b. one
c. two
d. three
e. four

Can any one explain on this please.?

User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Sat Sep 27, 2008 2:02 pm
Location: San Jose, CA
Thanked: 43 times
Followed by:1 members
GMAT Score:720

by dumb.doofus » Sat May 16, 2009 11:28 pm
I think there's jsut two 64 and 96 (post edited)
Last edited by dumb.doofus on Sun May 17, 2009 12:33 am, edited 1 time in total.
One love, one blood, one life. You got to do what you should.
https://dreambigdreamhigh.blocked/
https://gmattoughies.blocked/

Junior | Next Rank: 30 Posts
Posts: 11
Joined: Sat May 16, 2009 5:09 am

by bharatv » Sat May 16, 2009 11:40 pm
The OA seems to be C(Two)

But how did you calculate. Is there a easy way to do this?

Legendary Member
Posts: 1035
Joined: Wed Aug 27, 2008 10:56 pm
Thanked: 104 times
Followed by:1 members

by scoobydooby » Sun May 17, 2009 12:28 am
figured out the other: 96 :)

2^5*3=96

User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Sat Sep 27, 2008 2:02 pm
Location: San Jose, CA
Thanked: 43 times
Followed by:1 members
GMAT Score:720

by dumb.doofus » Sun May 17, 2009 12:32 am
yeah :-) missed out on this one. ;-)

I don't see a simpler way other than just checking it manually..
One love, one blood, one life. You got to do what you should.
https://dreambigdreamhigh.blocked/
https://gmattoughies.blocked/