<PRE><B>Question 245303</B>
A book shelf containing 20 books of which 12 are on circuit theory and 8 are on Mathematics. If three books are taken out at random, find the probability that all the three are on the same subject.
--------------------------------
# of ways to get 3 of the same kind: 12C3 + 8C3 = 220 + 56 = 276
------------------
# of possible sets of 3: 20C3 = 1140
-----------------------
Probability = 276/1140 = 0.242
=====================================
Cheers,
Stan H.</PRE>