Hard Probability question (1 Viewer)

[rama_v]

A bag contains 4 red and 3 green apples. peter took two apples at random. If it is known that at least one of the apples is red, find the probability that they are both red.

Answer: 6/17 (apparently).Unfortunatley I cant get the answer, can someone please show me? Thanks

 

[Riddles]

what answer do u get?

 

[Jumbo Cactuar]

I always get 1/3.

 

[rusty_rouge]

A bag contains 4 red and 3 green apples. peter took two apples at random. If it is known that at least one of the apples is red, find the probability that they are both red.

Answer: 6/17 (apparently).Unfortunatley I cant get the answer, can someone please show me? Thanks

Um - is that a typo? Coz I keep getting 6/7. Did you do it with replacement? Because I'm doing without, and I'm pretty sure its right - we had a question like this in our half-yearly.

 

[rusty_rouge]

Here's thwe working - I used a probability tree, and sorry - I can't find a multiplication sign anywhere....

 

[Jumbo Cactuar]

Um - is that a typo? Coz I keep getting 6/7. Did you do it with replacement? Because I'm doing without, and I'm pretty sure its right - we had a question like this in our half-yearly.

That is the probability that at least one is Red, which is given;

The problability of 2 Red is 2/7 for the entire tree, but at least one is red. So the answer should be (2/7)/(6/7) = 2/6 = 1/3

 

[shafqat]

Here's thwe working - I used a probability tree, and sorry - I can't find a multiplication sign anywhere....

thats not quite right
the sample size you have to consider only includes the combinations RG, GR, and RR, but not GG.

I think I get 1/3 too, though I could be wrong cos I suck at probablity.

 

[Jago]

That's not what the question was asking rusty. You were suppose to find the probability of TWO reds when you know there is at least ONE red.

that being said, I got 1/3 as well. I've attached a diagram showing how i got what i got. black dots over ( black + blue dots ).

 

[FinalFantasy]

i hate probability!! dey should take it out of da syllabus, right NOW!

 

[rama_v]

I keep getting 1/3 as well. This was in a ruse paper, 1998 trial 2 unit. I have uploaded the paper so you guys can check. Also thanks for the input, its greatly appreciated

 

[rusty_rouge]

That's not what the question was asking rusty. You were suppose to find the probability of TWO reds when you know there is at least ONE red.

that being said, I got 1/3 as well. I've attached a diagram showing how i got what i got. black dots over ( black + blue dots ).

Ta! Lol - see why maths isn't my strongest subject? And yes, I think probability sucks too - the theory is easy, and the questions are dumb...

New plan: move on, and find a less sucky question!

 

[rama_v]

Ta! Lol - see why maths isn't my strongest subject? And yes, I think probability sucks too - the theory is easy, and the questions are dumb...

New plan: move on, and find a less sucky question!

Agreed!