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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: Solve this silly question
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[Post New]5 Mar 2008 13:39:53 IST
    Subject: Solve this silly question
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pantpranav (352)

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A student is allowed to select atmost n books from a collection of (2n + 1) books.
If the total number of ways in which he can select atleast 1 book are 63, find the value of n.
    
[Post New]5 Mar 2008 13:54:35 IST
    Subject: Re:Solve this silly question
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akhil_o (2704)

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2n+1C1+2n+1C2+....2n+1Cn
=22n+1-1-1
=22n-1=63
22n=26
so n=3
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[Post New]5 Mar 2008 14:24:58 IST
    Subject: Re:Solve this silly question
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kishore.subramanian.b (194)

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no of books:        0           1        2       ..........       n   
total selections:2n+1C0   2n+1C1   2n+1C2 ..............     2n+1Cn
(1+1)2n+1=2n+1C0 +2n+1C1   +  2n+1C2 ..............   +2n+1Cn +.............2n+1C2n+1
22n+1=2(2n+1C0 +2n+1C1   +  2n+1C2 ..............   +2n+1Cn )
22n=2n+1C0 +2n+1C1   +  2n+1C2 ..............   +2n+1Cn ...........(1)
given 2n+1C1   +  2n+1C2 ..............   +2n+1Cn =63
 Hence 22n=1 +63          from (1)
         Hence n=3
 
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