<PRE><B>Question 941516</B>
A BAG CONTAIN 80 BALLS NUMBERED 1,...,80. 
Before the game starts, you choose 10 different numbers from among 1,..80 and write them on piece of paper. 
Then 20 balls are selected with out replacement out of the bag at random. 
-------------------
1) what is the probability that all your numbers are selected?
# of ways to succeed:: 10C10*70C10
# of possible sets of 20:: 80C20
Ans:: [10C10*70C10]/80C20 = 0.24094
-----------------------------------------
 2)what is the probability that none of your numbers is selected?
Ans:::: 70C20/80C20 = 0.2494

 3) what is the probability that exactly 4 of your numbers are selected?
(10C4*70C16)/(80C20) = 0.1473
----------------
Cheers,
Stan H.
================
 </PRE>