Answer:
20
Step-by-step explanation:
One pattern is that we are adding one row and one column for each step.
The first step has 1 row and 2 columns,
the second one has 2 rows and 3 columns,
and the third has 3 rows and 4 columns.
Thus, it would make sense for the fourth step to have 4 rows and 5 columns. This makes a rectangle with a length and a width, with the area of the rectangle being length * width. 4 * 5 = 20 as our number of dots
