A bag contains 3 red, 5 yellow and 7 green balls. 3 balls are drawn randomly. What is the probability that the balls drawn contain balls of different colours?  Choose the correct choice from the following choices.
A) 2/7
B) 3/5
C) 3/13
D) 1/4
E) 7/16
Total number of balls = 3+5+7= 
<gadget id="calculator">3+5+7</gadget>
<output>15</output>
15   n(S)= 153/133 = 455   n(E) = 33/131 * 53/131 * 73/131 = 105   Probability = 105/455 = 3/13   Answer is 3/13
<result>C</result>
A bag contains 3 red, 5 yellow and 7 green balls. 3 balls are drawn randomly. What is the probability that the balls drawn contain balls of different colours?