sgrtretregudgnfiudhg
Probability question for Letsrun: can you solve this problem? 4/12/2012 6:48PM Reply | Return to Index | Report Post
Can you solve this probability problem Letsrun?

You have 4 questions, each worth 6 points (and you can get from 0 to 6 on these). How many different ways can you get 20 points?
yagtash
RE: Probability question for Letsrun: can you solve this problem? 4/12/2012 6:56PM - in reply to sgrtretregudgnfiudhg Reply | Return to Index | Report Post
6 6 6 2
6 6 2 6
6 2 6 6
2 6 6 6


6 6 5 3
6 5 6 3
5 6 6 3
6 6 3 5
6 5 3 6
5 6 3 6
6 3 6 5
6 3 5 6
5 3 6 6
3 6 6 5
3 6 5 6
3 5 6 6

6 6 4 4
6 4 6 4
4 6 6 4
6 5 5 4
5 6 5 4
5 5 6 4
6 4 4 6
4 6 4 6
5 5 4 6
5 fvck this im bored.
gromes
RE: Probability question for Letsrun: can you solve this problem? 4/12/2012 7:41PM - in reply to sgrtretregudgnfiudhg Reply | Return to Index | Report Post
I did it with generating functions...

and got 1372.

Solved it pretty quickly (read: haphazardly) but I believe this is correct.
fiftypence
RE: Probability question for Letsrun: can you solve this problem? 4/12/2012 7:58PM - in reply to sgrtretregudgnfiudhg Reply | Return to Index | Report Post
The answer is 7 choose 3 I believe
(You have to split 4 missed points over 4 problems. That is 4 multichoose 4 which reduces to 7 multichoose 3)

So 7!/(3!4!)=7*6*5/(3!)=7*5=35

More brute force
Miss all on one question=4 ways
Miss 3 on one, 1 on one=12 ways
Miss 2 on one, 1 on two others=12 ways
Miss 2 on 2 of them=6 ways
Miss 1 on all four =1 way
=35

BTW this is combinatorics not probability.
sdlmsdkl
RE: Probability question for Letsrun: can you solve this problem? 4/12/2012 8:07PM - in reply to fiftypence Reply | Return to Index | Report Post
Shit I thought it was 6 questions, 6 points each and 20 points total, which was way too hard for me to figure out
gromes
RE: Probability question for Letsrun: can you solve this problem? 4/12/2012 8:28PM - in reply to sdlmsdkl Reply | Return to Index | Report Post
apparently, I cannot do algebra...

But 35 is correct