Question

Tim throws a fair die twice and notes the number on each throw.
He calculates his final score as follows: If the number on the second throw is a 5, he multiplies the two numbers together, and if the number on the second throw is not a 5, he adds the two numbers together. Find the probability that his final score is
a) 12
b) 5

Answer 1

There are 36 possibilities for the 2 dice. Right?
11 12 13 14 15 16
21 22 ......................
................................
6*6= 36
a) Figure out which of the 36 combinations result in 12. We can never make a 12 by multiplying a second roll of 5 times something. 5 is not a factor of 12. We can make 12 by adding the 2 number. Only one combination works: 66
That's one combination out of 36
1/36 or
.0278

Answer 2

Oh, okay. Got that one.

Answer 3

b) To get a 5, we could get 15...that would work. 2nd number is a 5, multiply to get 5
Also: 14 23 32 41....those four work also
5 combinations work
5/36 or .1389

Answer 4

Oh, that's awesome. Thank you so much. ^_^ I was interpreting it all wrong. Now I get it. :D