A bag contains 2 red, 3 green and 2 yellow balls. Two balls are drawn at random. What is the probability that none of the balls drawn is yellow? Choose the correct choice from the following answers:  A) 10/15  B) 10  C) 11  D) 10/21  E) 10/23
Total number of balls = (2 + 3 + 2)= 
<gadget id="calculator">(2 + 3 + 2)</gadget>
<output>7</output>
7.   Let S be the sample space.   Then, n(S)= Number of ways of drawing 2 balls out of 7   = 7C2 `   = (7 x 6)/(2 x 1)   = 21.   Let E = Event of drawing 2 balls, none of which is yellow.   n(E) = Number of ways of drawing 2 balls out of (2 + 3) balls.   = 5C2   = (5 x 4)/(2 x 1)   = 10.   P(E) = n(E)/n(S) = 10/21   Hence answer is 10/21
<result>D</result>
A bag contains 2 red, 3 green and 2 yellow balls. Two balls are drawn at random. What is the probability that none of the balls drawn is yellow?