## Probability: What do "and" and "or" mean?

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hatesmath2011
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### Probability: What do "and" and "or" mean?

Hello I need help on probabilty...
First things first: What do "and" and "or" mean? I am confused if...and=multiplication | or=adding the two probabilities together.
Does mutually exclusive mean that the two events can't happen at the same time?
And I don't know what are overlapping/ independent/ dependent events....

A problem from my math packet:
2.There are two bags of coins. Each bag holds 1 nickel, 1 dime and 1 quarter. Choose one coin @ random from each bag. Find the probability of getting the following.
a) P(both are nickels)
b) P(exactly one nickel)
c) P(no nickels)
d) P(at least one dime)
e) P(all dimes)
f) P(at most one quarter)
g) P(both are same coins)
h) P(both are different coins)

Okay...so I got a,b, and c, but my friend did it, so I don't understand. a= 1/9, b=4/9, c=4/9. <--- Is that correct? If yes can you please explain it to me?

Thanks!

maggiemagnet
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Joined: Mon Dec 08, 2008 12:32 am
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### Re: Probability: What do "and" and "or" mean?

What do "and" and "or" mean? I am confused if...and=multiplication | or=adding the two probabilities together.
Maybe if you could provide a couple examples of what you mean...?
Does mutually exclusive mean that the two events can't happen at the same time?
Yes.
And I don't know what are overlapping/ independent/ dependent events....
Your book should have the definitions that you should use.
A problem from my math packet:
2.There are two bags of coins. Each bag holds 1 nickel, 1 dime and 1 quarter. Choose one coin @ random from each bag. Find the probability of getting the following.
a) P(both are nickels)
b) P(exactly one nickel)
c) P(no nickels)
d) P(at least one dime)
e) P(all dimes)
f) P(at most one quarter)
g) P(both are same coins)
h) P(both are different coins)

Okay...so I got a,b, and c, but my friend did it, so I don't understand.
What did you get? What was your reasoning?

Martingale
Posts: 333
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA
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### Re: Probability: What do "and" and "or" mean?

Hello I need help on probabilty...
First things first: What do "and" and "or" mean? I am confused if...and=multiplication | or=adding the two probabilities together.
$A$ and $B$ independent if and only if $P(A\text{ and }B)=P(A)\cdot P(B)$

if $A$ and $B$ are mutually exclusive then $P(A\text{ or } B)=P(A)+P(B)$

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