Conditional Probabilities problem

  • #1
1. Homework Statement ******* SOLVED *********

There are three magazines A,B and C respectively. A survey of readers was taken and the following data was collected.

0.6 Read A
0.5 Read B
0.5 Read C
0.3 Read A&B
0.2 Read B&C
0.3 Read A&C
0.1 Read A&B&C

What is the probability that a reader reads two magazines exactly?

Homework Equations

P(R|Q) = P(Q n R) / P(Q) = probability of R given Q. where R,Q are events.

The Attempt at a Solution

I attempted this by just using logic. I thought that readers who read A&B,B&C,A&C but not all three magazines would be the solution: giving a probability of 0.5 which I believe is correct.

I assume conditional probability is meant to be used in the solution but I am unable to see how the sums fit. Any help would be much appreciated.
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  • #2
It is easy to solve by the Venn diagram.

  • #3
thanks ehild, that's pretty much how I did it. I thought there was more to it, I was looking for unicorns and finding donkeys.

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