Question

Anyone good at algebra two? I am doing conditional probability and cannot figure out how to get the correct answer on a certain question. It says "a box contains three blue marbles, five red marbles, and four white marbles. If one marble is drawn at random, find P(not red l not white). The correct answer is 3/8 but I'm so lost.

Answer 1

Given events A and B,
\[P(A|B)=\frac{ P(A and B) }{ P(B) }\]

Answer 2

In this case, event A is the event of getting not red, event B in the event of getting not white

Answer 3

Helpful?

Answer 4

I would use 7/12 over 8/12 ? is that correct ?

Answer 5

@bobo-i-bo

Answer 6

So you're saying P(A and B)=7/12 and P(B)=8/12?

Answer 7

yea, I guess so.

Answer 8

I understand most of this unit, just this one question I don't understand

Answer 9

hmmm, so you are wrong for P(A and B). P(A and B)=P(not red and not white) which is the probability of getting any colour but red or white.

Answer 10

oh oh oh, ok, I think maybe I understand. Let me try it and see

Answer 11

Omg, i got it, thank you so much! haha

Answer 12

:)