QumaCote Posted May 16, 2012 Share Posted May 16, 2012 All Ye Brilliant Math Minds, I would really appreciate help with a math problem. I am too tired and too math deficient to trust my answer. Problem: How many combinations can you get with the following? A1....A10 B1....B4 C1....C4 D1....D4 E1....E4 Each combination will include an A_, B_, C_, D_, E_ but order does not matter. This is not a problem from a book. My husband is trying to figure out something at work. Thanks for your help!! Quote Link to comment Share on other sites More sharing options...
Belacqua Posted May 16, 2012 Share Posted May 16, 2012 I just assigned your problem. I'm told the answer is 2,560. :) Quote Link to comment Share on other sites More sharing options...
QumaCote Posted May 16, 2012 Author Share Posted May 16, 2012 Can you tell me how you solved it? I was getting a much higher number. Thanks for the speedy math minds! My brain is positively fried today!! Quote Link to comment Share on other sites More sharing options...
Belacqua Posted May 16, 2012 Share Posted May 16, 2012 Can you tell me how you solved it? I was getting a much higher number. Thanks for the speedy math minds! My brain is positively fried today!! According to Local Combinatorics Guy: There are 10 ways to choose A, 4 ways for all the others. Thus we multiply 10x4x4x4x4=2560. It could be larger if "each combination includes an A..." means "at least one A," etc. If you're allowing more than one of each letter per combination, you'd get 1,023 x 15 to the fourth (I don't know how to do exponents here) which is, according to LCG, a complete mess: 51,789,375. Quote Link to comment Share on other sites More sharing options...
wapiti Posted May 16, 2012 Share Posted May 16, 2012 There are AoPS videos for this also. Counting with Multiplication Part 1 Counting with Multiplication Part 2 If this doesn't answer his question, see the other counting videos as well. Quote Link to comment Share on other sites More sharing options...
QumaCote Posted May 16, 2012 Author Share Posted May 16, 2012 Thank you both for your help! I feel so completely inadequate some days--I'm glad there are helpful people here with functioning brain cells. Have a beautiful day! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.