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# S1 probability venn diagrams(any answers appreciateD) watch

1. A patient going in to a doctor's waiting room reads Hiya magazine with a probability 0.6 and Dakor magazine with probability 0.4. The probability the patient reads either one or both of the magazines is 0.7. Find the probability the patient reads:
a)both magazines
b)Only Hiya
2. For part a), have you tried playing around with the addition rule using the information you know?
For part b), once you have part a), and you draw the venn diagram, the answer should become fairly obvious.
3. (Original post by gcsemusicsucks)
For part a), have you tried playing around with the addition rule using the information you know?
For part b), once you have part a), and you draw the venn diagram, the answer should become fairly obvious.
Not sure what you mean for part a. I started probability today and finding it pretty hard. If I were to add the probabilities of the books , 0.6+0.4=1. My main issue is I don't know what the 1 means in the sense it's not the probability that the person reads either one of the books and I don't know what it could mean.

I get the probability that neither books are read is 0.3 and that the total probability that the person reads Hiya is 0.6(so the probability that the person reads JUST Hiya or BOTH Hiya and Dakor). But from that I don't know how you use the addition rule.
4. (Original post by dont know it)
Not sure what you mean for part a. I started probability today and finding it pretty hard. If I were to add the probabilities of the books , 0.6+0.4=1. My main issue is I don't know what the 1 means in the sense it's not the probability that the person reads either one of the books and I don't know what it could mean.

I get the probability that neither books are read is 0.3 and that the total probability that the person reads Hiya is 0.6(so the probability that the person reads JUST Hiya or BOTH Hiya and Dakor). But from that I don't know how you use the addition rule.
You're right in the fact that 0.6+0.4=1 - that's always the case, as the total probabilities always add up to 1. The addition rule is something different, maybe you haven't come across it but you will soon and it's extremely helpful in answering these questions. The rule is:

the probability of either A or B = probability of A + probability of B - probability of A and B

You know P(either A or B)=0.7, P(A)=0.6 and P(B)=0.4, so just sub this into the equation and rearrange to get P(A and B), which is the probability of both magazines being read.
5. (Original post by gcsemusicsucks)
You're right in the fact that 0.6+0.4=1 - that's always the case, as the total probabilities always add up to 1. The addition rule is something different, maybe you haven't come across it but you will soon and it's extremely helpful in answering these questions. The rule is:

the probability of either A or B = probability of A + probability of B - probability of A and B

You know P(either A or B)=0.7, P(A)=0.6 and P(B)=0.4, so just sub this into the equation and rearrange to get P(A and B), which is the probability of both magazines being read.
Thanks for helping me greatly! Didn't know that but thanks to you I do now.
6. (Original post by dont know it)
Thanks for helping me greatly! Didn't know that but thanks to you I do now.

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