An urn contains four balls: one red, one green, one yellow, and one white. Two balls are drawn without replacement from the urn. What is the probability of getting a red ball and a white ball? Assume that the balls are equally likely to be drawn

Here's what I've tried:

Probability of a red or a white ball on first draw: $\frac{1}{4}$

Probability of a red or a white ball on second draw: $\frac{1}{3}$

Total Probability : $\frac{1}{4}\cdot\frac{1}{3}=.0833$, but the correct answer is $0.167$

  • $\begingroup$ There are two balls at the start which are acceptable. so the odds are $\frac{2}{4}=\frac{1}{2}$ $\endgroup$
    – Asinomás
    Dec 17, 2013 at 23:38

1 Answer 1


Probability of getting a red or white ball on first draw:$\frac{1}{2}$

probability of getting the remaining ball that is either red or white $\frac{1}{3}$

probability both of these happen: $\frac{1}{2}\cdot \frac{1}{3}\approx0.167$


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