today im showing you how to do probability with combinations. its kind of hard to explain this method without showing an example. you have to use the combinaion formula which is (n! / (n-r)! r!). usually this type of stuff will be dealing with more than one thing such as a 52 deck of cards and dice and things of that sort. it will be really easy to explain once i show the examole below. so here we go.
EX: free concert tickets are distributed to 4 students chosen at random from 8 Jrs. and 12 Srs. in the school orchestra. what is the probability that free tickets are recieved by:
a) 4 senoirs
first put in combination form: 12 C 4 / 20 C 4
it is like this because there are 12 senoirs and your choosing 4 andd there is a total of 20 people
this is your answer in combination form.
b) exactly 3 seniors
put in combination form: 12 C 3 * 8 C 1 / 20 C 4
this is your answer in combination form because your choosing 3 senoirs and multiply by it the chance of getting one junior over the total
c) exactly 2 senoirs
12 C 2 * 8 C 2 / 20 C 4
combination form answer ^
d) exactly 1 senior
12 C 1 * 8 C 3 / 20 C 4
combination form answer ^
e) no seniors
8 C 4 / 20 C 4
combination form answer ^
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