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**Hannibal lecter****Member**- Registered: 2016-02-11
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Hi, two dice are thrown, fine the probability that the sum is 8 if you know one of them is 5

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**bob bundy****Administrator**- Registered: 2010-06-20
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Hi,

Out of the 36 outcomes for two dice, how many have a five ? And of those, how many give a total of eight ?

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**Hannibal lecter****Member**- Registered: 2016-02-11
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there is 2,

do you mean the solution is 2/36??????????? really just that?

Wisdom is a tree which grows in the heart and fruits on the tongue

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The denominator will not be 36. Remember: you want to restrict the number of possible outcomes to include only those that have a '5' in them.

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**Hannibal lecter****Member**- Registered: 2016-02-11
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then what is the denominator ?

Wisdom is a tree which grows in the heart and fruits on the tongue

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**Hannibal lecter****Member**- Registered: 2016-02-11
- Posts: 225
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are you there bob bundy, can you tell what is the denominator value please is it 36 or not

Wisdom is a tree which grows in the heart and fruits on the tongue

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**bob bundy****Administrator**- Registered: 2010-06-20
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I think it's this:

36 possibilities of which 11 have a five:51, 52, 53, 54, 55, 56, 15, 25, 35, 45, 65 don't count 55 twice.

Of these 53 and 35 add to eight.

So P = 2/11

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**Hannibal lecter****Member**- Registered: 2016-02-11
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you are too late, my answer in the exam was p = 2 / (36-4)

Wisdom is a tree which grows in the heart and fruits on the tongue

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**Hannibal lecter****Member**- Registered: 2016-02-11
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you two were be able to give me the value of the denominator before the exam is finish,

but you didn't help me,

are you always answer the questions in this way ?

Wisdom is a tree which grows in the heart and fruits on the tongue

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,386

hi Hannibal lecter

I'm sorry you didn't get what you wanted in time for your exam. What you have to realise is that MIF is a world wide, and free to use, forum. While you are studying, the person helping you may be sleeping, or at work, or just digging the garden.

When you know you have an exam approaching you need to allow plenty of time for other members to respond. I'm surprised that you knew in advance what question would be asked. This doesn't happen in the UK; candidates can practise similar questions but the examiners set new questions for the exam itself. Had I known this I would have been even more reluctant to provide the actual answer since it goes against what I believe is the purpose of the exam in the first place. If you give an answer having no idea why it is correct but just copying someone else then you give the examiners a false impression of your understanding.

This is why I try to provide general help on the topic rather than just a model answer. It says in the rules: "This is a Forum, it is not instant chat. Leave your message, and come back later (hours or days) to see what responses you got." And in the advice when asking for help: "We are happy to help! But we don't do your homework for you." This could equally have said: "We won't do your exam for you."

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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