Question

A square is divided into 9 identical smaller squares. six identical balls are to be placed in these smaller squares such that each of the three rows gets at least one ball (one ball in one square only). in how many different ways can this be done?

Answer 1

This is the solution to this question...

⁹C₆−⁶C₆ = 83

⁹C₆ are the total ways in which the squares can be selected

We subtract the case in which the 6 balls go into the six squares of two rows...