A bag contains 7 green and 8 white balls. If two balls are drawn simultaneously, the probability that both are of the same colour is Choose the correct choice from the following answers
A) 7 / 16 B) 7 / 12 C) 7 / 19 D) 7 / 12 E) 7 / 15

Rationale: "drawing two balls of same color from seven green balls can be done in ⁷ c ₂ ways . similarly from eight white balls two can be drawn in ⁸ c ₂ ways . p = ⁷ c ₂ / ¹ ⁵ c ₂ + ⁸ c ₂ / ¹ ⁵ c ₂ = 7 / 15 answer : e"
Answer: E