SOLUTION: In a bag there are 20 red marbles and 15 black ones. By no replacement, find the probability that randomly selecting four marbles, they are all red.

Question 309422: In a bag there are 20 red marbles and 15 black ones. By no replacement, find the probability that randomly selecting four marbles, they are all red.
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
20 R, red
15 B, black
35 total to start
P(R)=20/35=4/7
w/o replacement
P(R)=19/34
w/o replacement
P(R)=18/33=6/11
w/o replacement
P(R)=17/32
Multiply the probabilities,
P(R,R,R,R)=(4/7)(19/34)(6/11)(17/32)
P(R,R,R,R)=(19*3)/(7*2*11*4)
P(R,R,R,R)=57/616
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