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# Probability. watch

1. This may well seem too simple but how would i work out the probability of rolling a "4" and then a "6". using P(4 or 6)=P(4) + P(6). Using this i came to the answer of 2/6 but that would mean that the probability is now greater than rolling just one 4 or 6. or am i confusing myself? shouldn't i be multiplying 1/6 * 1/6 or is that something else?
2. it's 1/6 * 1/6 so 1/36

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3. P(4 or 6) is not equal to P(4) -> P(6) (as in rolling one then the other)
P(4 or 6) would be the probability of rolling either a 4 or a 6 given only one roll.
4. (Original post by Salman_)
it's 1/6 * 1/6 so 1/36

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yes but how so? can you please analyse this formula for me?

p(a or b)= p(A) + p(B)

why is this a plus and not a multiplication symbol?
i'm very confused.

the "+" is what's confusing me.
5. I don't know why, I just know the answer. sorry.

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6. (Original post by WarHammer-)
yes but how so? can you please analyse this formula for me?

p(a or b)= p(A) + p(B)

why is this a plus and not a multiplication symbol?
i'm very confused.

the "+" is what's confusing me.
Take this example,
On a fair dice, you have 6 possible outcomes. If you throw the dice, what is the probability that you'll land on either a 1 or 2 or 3 or 4 or 5 or 6?
7. (Original post by Salman_)
I don't know why, I just know the answer. sorry.

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That's quite alright mate! i had the same answer as you but i just didn't know why! lol someone might explain this phenomenon to me if not you!

thanks for trying.
8. (Original post by IDontKnowReally)
Take this example,
On a fair dice, you have 6 possible outcomes. If you throw the dice, what is the probability that you'll land on either a 1 or 2 or 3 or 4 or 5 or 6?

1/6.
9. (Original post by WarHammer-)
1/6.
What must the total probability add up to?
10. (Original post by IDontKnowReally)
What must the total probability add up to?
6.
11. (Original post by WarHammer-)
6.
No. The total probability always adds up to 1. Your teacher should have taught you this?
12. (Original post by IDontKnowReally)
No. The total probability always adds up to 1. Your teacher should have taught you this?
oh yes i know that sorry my bad.
13. (Original post by WarHammer-)
oh yes i know that sorry my bad.
Okay, so you know that the probability of each outcome is 1/6, and the total probability adds up to 1.
You also know that there are 6 possible outcomes.
Everytime you roll a dice you get one of those outcomes (you get a 1 OR you get a 2 OR a 3 OR 4 OR 5 OR 6).
1/6 + 1/6 + 1/6 +... = 1
so P(1 OR 2 OR 3 OR 4 OR 5 OR 6) =1
14. (Original post by IDontKnowReally)
Okay, so you know that the probability of each outcome is 1/6, and the total probability adds up to 1.
You also know that there are 6 possible outcomes.
Everytime you roll a dice you get one of those outcomes (you get a 1 OR you get a 2 OR a 3 OR 4 OR 5 OR 6).
1/6 + 1/6 + 1/6 +... = 1
so P(1 OR 2 OR 3 OR 4 OR 5 OR 6) =1
so is post number 2 correct?
15. (Original post by WarHammer-)
so is post number 2 correct?
Yes, it is. Do you understand why?
16. [QUOTE=IDontKnowReally;68398152]Yes, it is. Do you understand why?[/QUOTE

(1/6)^2 because of two activities going on?
17. [QUOTE=WarHammer-;68398236]
(Original post by IDontKnowReally)
Yes, it is. Do you understand why?[/QUOTE

(1/6)^2 because of two activities going on?
Yes

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