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December 1st, 2010, 01:09 PM  #1 
Newbie Joined: Oct 2010 Posts: 10 Thanks: 0  Please help with this math problem including primes
Let the letters p, q, and r represent different primes. Then p^2 qr^3 has 24 divisors. So would p^23. Use p, q, and r to describe all whole numbers having exactly the following number of divisors. (a) 2 (b) 3 (c) 4 (d) 5 (e) 6 (f) 12 
December 1st, 2010, 03:26 PM  #2 
Senior Member Joined: Nov 2010 From: Staten Island, NY Posts: 152 Thanks: 0  Re: Please help with this math problem including primes
(a) (b) (c) (d) (e) (f) , , , In general, we get these by looking at all factorizations of the number, and using k1 as an exponent for each factor k. For example, the factorizations of 12 are 12*1, 6*2, 4*3, and 3*2*2 
December 1st, 2010, 04:31 PM  #3  
Math Team Joined: Dec 2006 From: Lexington, MA Posts: 3,267 Thanks: 408  Re: Please help with this math problem including primes Hello, sophieT66! Quote:
[color=red]**[/color] [color=beige]. . [/color]  
December 2nd, 2010, 12:04 PM  #4 
Senior Member Joined: Nov 2010 From: Staten Island, NY Posts: 152 Thanks: 0  Re: Please help with this math problem including primes
Good post Soroban, but one small correction: pqr has 8 divisors, not 6. 
December 2nd, 2010, 04:41 PM  #5 
Math Team Joined: Dec 2006 From: Lexington, MA Posts: 3,267 Thanks: 408  Re: Please help with this math problem including primes Thanks for the headsup, Dr.Steve ! Hello, Moderators: We don't have an EDIT capability? 
December 2nd, 2010, 04:55 PM  #6 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: Please help with this math problem including primes
The editing of posts was recently increased from 1 hour to 12 hours after the post is made. I'm sure [color=#BF0000]julien[/color] has a good reason for imposing a time limit on post editing. I edited your post. 

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