The solution to 1997 9a)iv? (1 Viewer)

[addikaye03]

Can someone tell me why they believe it is 1/5 when it has to be 1/3. Since the red ball is dropped the first ball must be red therefore must be RR, RB or RW NOT RB, RR, RW, BR, BW as the success one books published the answer. Therefore P(RR) = 1/3 NOT 1/5

If i'm wrong, please explain why?

 

[lyounamu]

Can someone tell me why they believe it is 1/5 when it has to be 1/3. Since the red ball is dropped the first ball must be red therefore must be RR, RB or RW NOT RB, RR, RW, BR, BW as the success one books published the answer. Therefore P(RR) = 1/3 NOT 1/5

If i'm wrong, please explain why?

It will be great if you could post up the question.

 

[addikaye03]

It will be great if you could post up the question.

lol yer, fair enuf...

Q) A bag contains two red balls, one black ball, and one white ball. Andrew selects one ball from the bag and keeps it hidden. He then selects a second ball, also keeping it hidden.

i) Draw a tree diagram to show all possible outcomes
ii) Find the probability that both the selected balls are red
iii) Find probabilty that at least one of the selected balls is red
iv) Andrew drops one of the selected balls and we see that it is red. What is the probability that the ball that is hidden is also red?

i wrote the whole thing as u may need previous parts for the part iv)

 

[henry08]

Can someone tell me why they believe it is 1/5 when it has to be 1/3. Since the red ball is dropped the first ball must be red therefore must be RR, RB or RW NOT RB, RR, RW, BR, BW as the success one books published the answer. Therefore P(RR) = 1/3 NOT 1/5

If i'm wrong, please explain why?

I just done it and I get the same as them (RW NOT RB, RR, RW, BR, BW), so 1/5 would be correct.

 

[lyounamu]

lol yer, fair enuf...

Q) A bag contains two red balls, one black ball, and one white ball. Andrew selects one ball from the bag and keeps it hidden. He then selects a second ball, also keeping it hidden.

i) Draw a tree diagram to show all possible outcomes
ii) Find the probability that both the selected balls are red
iii) Find probabilty that at least one of the selected balls is red
iv) Andrew drops one of the selected balls and we see that it is red. What is the probability that the ball that is hidden is also red?

i wrote the whole thing as u may need previous parts for the part iv)

No, it is one of the selected balls. And the ball that he dropped was initally one of the selected balls which means it was hidden.

 

[addikaye03]

No, it is one of the selected balls. And the ball that he dropped was initally one of the selected balls which means it was hidden.

sorry sorry, i think i missed a valuable word. The last part of iv) says " What is the probability that the ball that is STILL hidden is also red"

thanx again and sorry

 

[addikaye03]

ooooo.. i get it now, how silly of me to miss that, thanxs heaps for the assistance