A bag contains 4 blue, 5 white and 6 green balls. Two balls are drawn at random. What is the probability that one ball is white?
Pick one.
A) 3/4 B) 2/35 C) 1/2 D) 3/7 E) 10/21
1 white ball can be drawn from 5 white balls in 5C1 = 5 ways   1 ball from the remaining 10 balls can be drawn in 10C1 = 10 ways   Hence, one white ball and one other colour ball can be drawn in 5 × 10 = 50 ways   i.e.,n(10/21) = 50   n(S) = Number of ways in which 2 balls can be drawn from 15 balls (∵ 4 + 5 + 6 = 15)   = 15C2   P(10/21) = n(10/21)/n(S)=50/15C2   =50(15×14/2×1)=50×2/15×14=10×2/3×14=10/3×7=10/21   ANSW10/21R:10/21
<result>E</result>
A bag contains 4 blue, 5 white and 6 green balls. Two balls are drawn at random. What is the probability that one ball is white?