You roll a number cube twice. What is the probability of rolling an even number and a 5?

2 Answers
May 4, 2018

1/616

Explanation:

P(even)=1/212

P(5)=1/616

So the probability of (even nn 5)=1/2xx1/6=1/12(even5)=12×16=112
But you could also get (5 nn even)1/12(5even)112

1/12+1/12=1/6112+112=16

May 4, 2018

6/36 = 1/6636=16

Explanation:

Before we calculate an answer, drawing a possibility space allows us to see all the 3636 outcomes of throwing a cube twice.
The grid shows the sum of the two throws.

The red values are those which have a 55 and and an even number

6|" "7" "8" "9" "10" "color(red)(11)" "126 7 8 9 10 11 12
5|" "6" "color(red)(7)" "8" "color(red)(9)" "10" "color(red)(11)5 6 7 8 9 10 11
4|" "5" "6" "7" "8" "color(red)(9)" "104 5 6 7 8 9 10
3|" "4" "5" "6" "7" "8" "93 4 5 6 7 8 9
2|" "3" "4" "5" "6" "color(red)(7)" "82 3 4 5 6 7 8
1|ul(" "2" "3" "4" "5" "6" "7)
color(white)(xxxx)1" "2" "3" "4" "5" "6

P(5 and "even") = 6/36 =1/6

Using a calculation:

P(5 and "even") = P(5, "even") " OR " P("even", 5)

= (1/6 xx 3/6) + (3/6 xx1/6)

=3/36 +3/36

=6/36

=1/6