if nC5=nC6, what is the value of n?
a)9
b)10
c)8
d)11

• as we know that..nCr=nCn-r
  so r=5 and n-r=6
  or n=6+r=6+5=11
• 8 years agoHelpfull: Yes(12) No(0)
• option d: 11
• 8 years agoHelpfull: Yes(2) No(0)
• Given that nC5 = nC6
  nCr = n! / ((n-r)!r!)
  n! / (n-5)!5! = n! / (n-6)!6!
  n.(n-1).(n-2).(n-3).(n-4).(n-5) / 5! = n.(n-1).(n-2).(n-3).(n-4).(n-5) .(n-6) / 6!
  on cancelling
  1 = (n-5)/6
  n = 11
• 8 years agoHelpfull: Yes(2) No(1)
• option d: 11
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• d) 11
  nCr=nCn-r
  so if r=5 then n-r will be 6
  there fore
  11C5=11C6
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• ans;5+6=11
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• 11
  coz........ncr=nc(n-r)
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• nCr= nCs
  
  r=s
  
  n=r+s
  
  n=5+6=11
• 8 years agoHelpfull: Yes(1) No(0)
• i did by trial and error method whr
  11c5= 11!/(6!*5!) and 11c6=11!/(5!*6!)
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• option d:11
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• 11 ans............
  
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• nCr ; 11C5=11C6
  here 11C5 can be written as 11C(11-5)=11C6
  now 11C6(L.H.s)=11C6(R.H.S)
  therefore n=11
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• n=6+5=11 nCr=nC(n-r)
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• ans is ....11
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• 11 is the ans.
  
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• 11 because 11c5=11c6....
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• answer d
  n=11 value the put
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• ans is 11 nCr=nCr-n
  
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• nC5=nC6
  from 11 if we subtract 5 and 6 the remaining also vice versa
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