sirinivas
Sep 14, 2010, 12:11 AM
if all the letters of word engineer be written at random,what is the probability that all the letters e are found together
ebaines
Sep 14, 2010, 06:17 AM
First, what's the probability that all three E's will start the word?  The word has 8 letters, of which three are E's, so the chance of the first letter being an E is 3/8.  The chance of the first two letters both being E's is 3/8 x 2/7.  And the chance of all three E's being together to start the word is 3/8 x 2/ 7 x 1/6.  However, you are interested in the 3 letter combo occurring anywhere, meaning it could be letters 1, 2 &3, or 2,3, & 4, or... or 6, 7 & 8.  So there are 6 ways that you can have all three E's together.  So final answer is:
 
6 x 3/8 x 2/7 x 1/6