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 ?
"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 ."
add(multiply(divide(7, add(7, 7)), divide(subtract(7, const_1), subtract(add(7, 7), const_1))), multiply(divide(subtract(7, const_1), subtract(add(7, 7), const_1)), divide(7, add(7, 7))))