if there r n As,n Bs,n Cs making 3n
letters
then no. of ways of selecting r letters
out of them
1.r belongs to [1,n]
a rc2
b r+1c2
c r+2c2
d none of these
2. r belongs to [n+1,2n+1]
a r+2c2-3 r-n+1c2
b rc2-3 r+n-1c2
c r+1c2-3 r+n-1c2
d rc2-3 r-n+1c2
3 r belongs to [2n+2,3n]
a r+2c2-2 r-n+1c2 + r-2nc2
b r+2c2-2 r-n+1c2 + 3 rc2
c r+2c2-2 r-n+1c2 + r-nc2
d r+2c2-2 r-n+1c2 + 3 r-2nc2
4 as selecting k letters ,then k is
a 3n-r
b n-r
c 2n-r
d none of these
5.is max. when n is even where (n<r<2n+1)
is
a 3(n+1)2+1
b (n+1)2
c [3(n+1)2+1]/4
d none of these
6 is max. when is odd and n< r< 2n+1 is
a 3[n+1]/4
b 3[n+1]2
c n[n+1]2/4
d none of these
Moderation Team
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