Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

There are 11 songs on a playlist, 5 are slow and 6 are fast. When the DJ plays a song it will not be played again. what is the probability that the first two songs are played slow?

share|cite|improve this question
Where is the Geometry here? – JB King Jun 4 '13 at 19:33

For the first track, there are 11 choices of song, of which 5 are slow. Thus there’s a 5/11 probability that the first track played will be slow.

Let’s suppose the first track is a slow song. For the second track, there are now 10 choices of song, of which 4 are slow. There’s thus a 4/10 = 2/5 probability that the second track played will be slow (given that the first track was slow).

Thus, the probability that the first two tracks played are slow is given by $$\frac{5}{11} \times \frac{2}{5} = \frac{2}{11}.$$ (Although I don’t see the geometrical aspect.)

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.