Quote:
Originally Posted by dipsleo88
how many different ways can 8 persons sit in 10 chairs in a row??
how many different ways can 8 persons sit in 4 chairs in a row,where more then one person can occupy a chair??
how many different ways can 5 letters be posted in 8 letter-box??
please xplain me each solution,by comparing these questions with each other....as i feel, they are solved with the same formulae,but the conditions are different.
cheers,
dips 
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I am not gud in P&C althogh i will try
how many different ways can 8 persons sit in 10 chairs in a row??
-> 1st person can sit in any of the 10 given chairs so 10 ways
2nd can sit on any of the remaining 9 chairs so 9 ways
similarly for 3rd,4th...till 8th person for which 3 chairs remain.
so total number of ways = 10*9*8......*4*3
if you see formula wise its just arrangement of 8 people in 10 chairs.
how many different ways can 8 persons sit in 4 chairs in a row,where more then one person can occupy a chair??
-->1st person can sit on any of the 4 chairs so 4 ways
2nd can sit on any of the 4 chairs so 4 ways...similarly for remaining 6 persons also
so total number of ways = 4^8
how many different ways can 5 letters be posted in 8 letter-box??
1st letter can be posted in any of the 8 letterbox so 8 ways
2nd letter can be posted in any of the 8 box so again 8 ways
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.
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.similarly for other 3 letters also
hence the total number of ways = 8^5
Hope this helps...!!