PS 14

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 484
Joined: Sun Jul 30, 2006 7:01 pm
Thanked: 2 times
Followed by:1 members

PS 14

by magical cook » Wed Nov 28, 2007 10:51 am
C(m,n) = m! / [(m-n)! n!] for nonnegative integers m and n, m ³ n. If C(5,3) = C(5,x) and x ¹
3, what is the value of x?
A. 0
B. 1
C. 2
D. 4
E. 5

Hi, somehow I got it wrong. hope someone could help...

User avatar
Legendary Member
Posts: 986
Joined: Wed Dec 20, 2006 11:07 am
Location: India
Thanked: 51 times
Followed by:1 members

Re: PS 14

by gabriel » Thu Nov 29, 2007 2:41 am
magical cook wrote:C(m,n) = m! / [(m-n)! n!] for nonnegative integers m and n, m ³ n. If C(5,3) = C(5,x) and x ¹
3, what is the value of x?
A. 0
B. 1
C. 2
D. 4
E. 5

Hi, somehow I got it wrong. hope someone could help...
According to the given information C(5,3)= 5!/(3!*2!) ... and C(5,x) = 5!/((5-x)!*x!) .. now if you compare the 2 denominators you will see that only x = 2 will give the values 3 and 2 (which is what we want if they have to be equal) in the denominator, so the answer is C, that is x = 2..

Regards

Master | Next Rank: 500 Posts
Posts: 484
Joined: Sun Jul 30, 2006 7:01 pm
Thanked: 2 times
Followed by:1 members

by magical cook » Thu Nov 29, 2007 7:43 am
Hi gabriel - got it - thanks!