Observe the given rectangle
How many minimum numbers of rows or columns we need to add to make it a square.
We can observe from the figure that the rectangle has 4 rows and 3 columns.
4×3=12 dots in it.
For a square, we must have an equal number of rows and columns.
To make it a square we must add one column , i.e., we need to add 4 dots.
Now rows and columns both becomes 4, and the number of the balls becomes 4×4=42=16