1.

Let `S={1,2,3ddot,9}dotFork=1,2, 5,l e tN_k`be the number of subsets of S, each containing five elements out ofwhich exactly `k`are odd. Then `N_1+N_2+N_3+N_4+N_5=?`210 (b)252 (c) 125(d) 126A. 210B. 252C. 126D. 125

Answer» Correct Answer - C
`N_(i) = ""^(5)C_(k) xx ""^(4)C_(5 - k)`
`N_(1) = 5 xx 1`
`N_(2) = 10 xx 4`
`N_(3) = 10 xx 6`
`N_(4) = 5 xx 4`
`N_(5) = 1`
`N_(1) + N_(2) + N_(3) + N_(4) + N_(5) = 126`


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