393] the number of subsets of A={a1,a2,a3,......,an} which contain even number of elements is ----------
1]n_{C_{4}} \;, n_{C_{5}} ,n_{C_{6}} are in AP. find the value of n
-
UP 0 DOWN 0 0 9
9 Answers
392] in a group of 8 girls, 2 girls are sisters. the number of ways in which the girls can sit such that the 2 sisters are not sitting together is -----
39394]the number of positive integers ≤100,000 which contain exactly one 2,one 5 and one 7 in theor decimal expansion is -------------
11>
2nC5=nC4+nC6
Solving this gives,
n2-21n+20=0
=> n= 20,1
since,n>6 , becoz we have nC6 in our eqn
n=20
[339]