The least positive integer n for which n−1C5+n−1C6<nC7 is
14
15
16
28
Since mCr−1+mCr=m+1Cr we can write the given inequality as
nC6<nC7
⇒ nC6 nC7<1 ⇒ 7n−6<1 ⇒ n>13
∴ the value of n is 14.