goodminton
New member
- Joined
- Sep 18, 2009
- Messages
- 2
Hello, thanks for taking the time to read the following query. Lets say there are 13 balls in a bag numbered 1-13. Before any balls are drawn I select 7 numbers and then 7 balls are drawn from the bag. I can work out the chances of all 7 selections being drawn (13choose7) . I can also work out the chances that say 3 of my 7 selections are drawn (7choose3*6choose4/13choose7). I CAN'T, however, work out the probability for the following scenario. Let's say again there are 13 numbered balls and 7 to be drawn out. What is the probabilty that if I only select 5 numbers initially before 7 are drawn, 3 of my selections are drawn? I would like to be shown how to work this out using binomials without having to list all the combinations which took me ages! thank you