probablility with balls part 2

• May 30th 2010, 01:12 PM
andyboy179
probablility with balls part 2
hi, this is my question:

A second bag also containing 3 red balls, 2 yellow balls and 1 blue ball, identical except for their colours.
Sandi picks one ball from the bag at random.

B) Given that Sandi does not pick a yellow ball, what is the probability that she picks a red.

would the probability that she picks a red be 3/6? or would it be 3/4 because you take 2 yellow balls from all the ball put to gether which is 6?

Thanks
• May 30th 2010, 01:23 PM
Quote:

Originally Posted by andyboy179
hi, this is my question:

A second bag also containing 3 red balls, 2 yellow balls and 1 blue ball, identical except for their colours.
Sandi picks one ball from the bag at random.

B) Given that Sandi does not pick a yellow ball, what is the probability that she picks a red.

would the probability that she picks a red be 3/6? or would it be 3/4 because you take 2 yellow balls from all the ball put to gether which is 6?

Thanks

If she chooses a ball, the probability of it being red is $\frac{3}{6}$

but given that she did not choose a yellow ball, we know that

she chose one of the other 4, so your second solution is correct.