honeill1
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Hello im doing some mock questions could someone help with below please?

On any day during the summer of 1979 the probability that it rained was 1/6 .

In 1989, because of climatic changes, the probability that it rained on any day during the summer was only 1/10 .

(a) Calculate the probability that any 3 days chosen at
random during the summer of 1979 were all wet?

(b) Calculate the probability that it rained on a particular
date during the summer of 1979 and was dry on the
same date in 1989.
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mqb2766
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(Original post by honeill1)
Hello im doing some mock questions could someone help with below please?

On any day during the summer of 1979 the probability that it rained was 1/6 .

In 1989, because of climatic changes, the probability that it rained on any day during the summer was only 1/10 .

(a) Calculate the probability that any 3 days chosen at
random during the summer of 1979 were all wet?

(b) Calculate the probability that it rained on a particular
date during the summer of 1979 and was dry on the
same date in 1989.
Any ideas? You could think of it as probability trees in both cases.
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LSEGrad100
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(Original post by honeill1)
Hello im doing some mock questions could someone help with below please?

On any day during the summer of 1979 the probability that it rained was 1/6 .

In 1989, because of climatic changes, the probability that it rained on any day during the summer was only 1/10 .

(a) Calculate the probability that any 3 days chosen at
random during the summer of 1979 were all wet?

(b) Calculate the probability that it rained on a particular
date during the summer of 1979 and was dry on the
same date in 1989.
Good question!

Assuming that the probabilities are independent you can solve them in the following way:
a) Since the weather is independent for all three days we can just multiply the probability
Spoiler:
Show
1/6 * 1/6 * 1/6 = 1/216


b) We use the same approach here only we need to change the probabilities.
Spoiler:
Show
The probability of rain in 1979 is 1/6 while the probability of no rain in 1989 is 1-1/10 which is 9/10. So we multiply these to get 1/6 * 9/10 = 3/20
Last edited by LSEGrad100; 2 months ago
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mqb2766
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(Original post by LSEGrad100)
...
Could you please edit and not post solutions, as per the forum sticky.
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LSEGrad100
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(Original post by mqb2766)
Could you please edit and not post solutions, as per the forum sticky.
you're asking me to delete the solution?

Isn't that what the forum is meant for?
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davros
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(Original post by LSEGrad100)
you're asking me to delete the solution?

Isn't that what the forum is meant for?
Forum rules expressly prohibit the posting of solutions - this isn't a "do my homework" service

We try to provide hints and guidance so that posters are able to reach solutions by themselves.
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LSEGrad100
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(Original post by davros)
Forum rules expressly prohibit the posting of solutions - this isn't a "do my homework" service

We try to provide hints and guidance so that posters are able to reach solutions by themselves.
oh alright sorry didn't know about that read the guidelines for future reference
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davros
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(Original post by LSEGrad100)
oh alright sorry didn't know about that read the guidelines for future reference
no problem
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