How do you put sixteen dots in 4 rows of 5?

Make them into a square. If you were to make the lines all go the same way, you would need 20 dots to make four rows of five, but if you put them in a square shape, the dots in the corners occur in two lines (ones going across and ones going down), like this: O O O O O O O O O O O O O O O O Four rows of five!