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 If a, b and c are the greatest values of Cp   19,Cq   20 and Cr   21 respectively, then: 11C9  19a+b+c=

 

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a
75
b
74
c
67
d
45

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detailed solution

Correct option is A

We know Cr   n is greatest at middle term(s) a=Cp   19=C10   19=C9   19,  b=Cq   20=C10   20, c=C6   21=C10   21=C11   21 Now, using  Cr  n=nr Cr-1  n-1,   we get  b=2 C9  19, c =2111×2010×C9  19 ⇒a+b+c =C  1991+2+4211=C9  19751111C9  19a+b+c=75


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