Question

No. Of ways in which 12 identical balls can be put in 5 different boxes in a row, if no box remains empty is

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

This is same as placing 4 sticks anywhere in the 11 gaps created by placing 12 balls in a row such that no 2 sticks are put in the same gap. Therefore we have 11 gaps and 4 sticks.
${}^{(n-1)}{C}_{r-1}$
= ${}^{\left(11\right)}{C}_4$