Question

consider rolling two dice.what is the probability that the sum is odd given that one dice shows a 3?

Answer 1

well, you could brute force this

Answer 2

so assuming it's a six sided dice...

Answer 3

there are six possibilities for the other die

Answer 4

3+1 = 4 [even] 3+2 = 5 [odd] 3+ 3 = 6 [even] 3+ 4 = 7 [odd] 3 + 5 = 8 [even] 3 + 6 = 9 [odd]

Answer 5

so you know the roll of one of the dice is a three

Answer 6

looks to me there are 3 options that get you odd, 3 that give you even

Answer 7

in sum

Answer 8

(so 3/6 possibilities for the second die to make an odd number) = 50%

Answer 9

ohhhhh ok i get it

Answer 10

that's generally how these work - you want to consider <success case>/<total possibilities> - especially given all possibilities are equally likely e.g. a fair die

Answer 11

oh wow i wish my teacher would have put it that way

Answer 12

good to hear, good luck!

Answer 13

thanks goin