SOLUTION: a jar contains nine marbles numbered 1-9. two marbles are randomly selected one at a time without replacement. what is the probability that a. 1 is selected first and then 9 b.

Algebra ->  Probability-and-statistics -> SOLUTION: a jar contains nine marbles numbered 1-9. two marbles are randomly selected one at a time without replacement. what is the probability that a. 1 is selected first and then 9 b.       Log On


   

Question 316248: a jar contains nine marbles numbered 1-9. two marbles are randomly selected one at a time without replacement. what is the probability that
a. 1 is selected first and then 9
b. the sum of the numbers selected is 4?
c. the sum of the numbers selected is 5?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
a)P(1)=1/9
P(9)=1/8
P(1 then 9)=P(1)*P(9)=1/72
.
.
.
b) (1,3) (3,1) are the only possible outcomes that sum to 4.
There are 72 (9*8) possible outcomes.
P(sum=4)=2/72=1/36
.
.
.
c)(1,4)(2,3)(3,2)(4,1) are the only possible outcomes that sum to 5.
P(sum=5)=4/72=1/18