urgent: probability (1 Viewer)

[koizora]

o

 

[oly1991]

try drawing a tree diagram

 

[FFC]

does ani1 have solution for these

!) a sample of 3 items is selected at random without replacement froma batcj of 10 items, 4 of which are defective. find the proability that there is at most one defective item in the sample

2) 3 cards are drawn at random from a pack of 52 playing cards. wat is the proability that 3 aces are drawn if the drawing is done
a) without replacement b) with replacement


3) in a raffle, 20 tickets are sold and there are 2 prizes. If i buy 5 ickets what is the proability that i win at least one of the prize


THNK YOU SO MUCH

Agreed with above, a tree diagram is the go for number one:

Pretty sure you end up with P=4(2/21) + (1/14) = 19/42

As for number 2, a T.D. is probably unnecessary:

a) P = 4/52 * 3/51 * 2/50
b) P = 4/52 * 4/52 * 4/52

3. And for this, method is up to you, I like using combination notation:

There are 20C2 combinations of the winners of the prizes - 20 tickets, 2 winners.
For you to NOT win a prize, the winners would have to come from the other 15 tickets, for which there are 15C2 combinations.

As such, P(winning) = 1 - 15C2/20C2 = 17/38


Hope that helps, any problems, please reply =)