A bag contains 6 green balls and 7 white balls. If two balls are drawn simultaneously, what is the probability that both balls are the same colour?	Select.
A) 2/7
B) 3/10
C) 5/11
D) 6/13
E) 11/21
The total number of ways to draw two balls is 13C2 = 78   The number of ways to draw two green balls is 6C2 = 15   The number of ways to draw two white balls is 7C2 = 21   P(two balls of the same colour) = 36/78 = 6/13   The answer is 6/13.
<result>D</result>
A bag contains 6 green balls and 7 white balls. If two balls are drawn simultaneously, what is the probability that both balls are the same colour?