math help please.

[savvysearch]

Hi,

if a florist has 3 yellow roses, 2 pink rose, 5 red roses, how many 3 rose arrangements are possible? A: 120

what is probability of getting two 4s in 5 tosses of a fair die?
A: (10*125)/36*215

thanks in advance!

 

[croco]

I am not too sure about the second one but the first one in answered as such. 10 total flowers
hence:
10!/3!(10-3)!, so:
10*9*8*7*6*5*4*3*2*1/(7*6*5*4*3*2*1)3*2*1
7 thru 1 is cancelled on numerator and denominator and u end up with 10*9*8/3*2*1 or 10*3*3*2*2*2/3*2*1 and again u can quicly cancel the common terms and end up with 10*3*2*2/1=120

 

[Balki]

savvysearch,
Look at the solution on this thread, the problem is similiar. Also understand how the answer is reached because these problems are all similiar. And I don't think you'll have this type of problems on the real one.

http://forums.studentdoctor.net/showthread.php?s=&threadid=81368