A bag contains 7 green balls and 7 white balls. If two balls are drawn simultaneously, what is the probability that both balls are the same colour? Choose the correct choice from the following:	A) 4 / 13	B) 6 / 13	C) 8 / 21	D) 11 / 21	E) 17 / 42

Rationale: "the total number of ways to draw two balls is 14 c 2 = 91 the number of ways to draw two green balls is 7 c 2 = 21 the number of ways to draw two white balls is 7 c 2 = 21 p ( two balls of the same colour ) = 42 / 91 = 6 / 13 the answer is b ."
Answer: B