Another Probability Question...Dice

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Gr8fu13

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Feb 13, 2011
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Two dice are rolled, find the probability that the sum is odd and the number on one of the dice is a 3.

a. 1/6
b. 3/36
c. 1/2
d. 1/12

I am not sure where to even beginning with this one. Should I try and use a tree diagram? The odds of rolling an odd number I would think would be 1/2 since the dice have an equal amount of even and odd numbers. But the probability of rolling a 3 I don't know. Would it be 2/12? but if that is the case how would I combine those to come up with one answer? I added them and came up with 2/3 but that is not an option....please help:( I would think that A and C are not an option right off the bat. But I am not sure how I would go about coming up with either of the other two answers.
 
Gr8fu13 said:
Two dice are rolled, find the probability that the sum is odd and the number on one of the dice is a 3.

a. 1/6
b. 3/36
c. 1/2
d. 1/12

I am not sure where to even beginning with this one. Should I try and use a tree diagram? The odds of rolling an odd number I would think would be 1/2 since the dice have an equal amount of even and odd numbers. But the probability of rolling a 3 I don't know. Would it be 2/12? but if that is the case how would I combine those to come up with one answer? I added them and came up with 2/3 but that is not an option....please help:( I would think that A and C are not an option right off the bat. But I am not sure how I would go about coming up with either of the other two answers.
Click to expand...

Let us see how many ways we can satisfy the condition:

(3,2), (3,4),(3,6), (2,3), (4,3), (6,3) ........that's it

Out of 36 possible cases - 6 of those will satisfy your criterion → probability of success = 6/36
 
So if that is the case, would I multiply the 1/2 for the probability of an odd number and the probabilty of a 3 (6/36) and come up with 1/12?
 
Thanks for the through explaination. I wasn't figuring in the fact about the odd numbers and rolling a 3 which IS an odd number:) The whole independant thing was confusing to me as well. I think I am going to have to go back and review more of the chapter again. I just don't understand it the way it is written. I did see the 39 vs. 40 on the other problem. I wouldn't have ever thought that 39 would be the denominator because there were 40 strings. Thanks for all your help.
 
I will definitely be bringing that up to my teacher for the sake of future students. Thanks!
 
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