A red ball and 18 white balls are in a box. If two balls are drawn, without replacement, what is the probability of getting 2 white W balls?
A) Pr(W first ∩ W second) =
B) Pr(W first ∩ W second) = 1
C) Pr(W first ∩ W second) =
D) Pr(W first ∩ W second) =
E) Pr(W first ∩ W second) =

Question

A red ball and 18 white balls are in a box. If two balls are drawn, without replacement, what is the probability of getting 2 white W balls? ​
A) Pr(W first ∩ W second) = 
B) Pr(W first ∩ W second) = 1 
C) Pr(W first ∩ W second) = 
D) Pr(W first ∩ W second) = 
E) Pr(W first ∩ W second) =

Quizplus · Accepted Answer

There are 18 white balls and 19 total balls in the box. So, the probability of drawing a white ball on the first draw is 18/19. Since we are not replacing the first ball before drawing the second one, there are now 17 white balls and 18 total balls left in the box. So, the probability of drawing a white ball on the second draw, given that the first ball was white, is now 17/18. Therefore, the probability of getting two white balls in a row is (18/19) x (17/18) = 306/342 = 0.895 or approximately 0.896. Therefore, the answer is C.

A Red Ball and 18 White Balls Are in a Box