How many wide?
How many squares does it contain?
If it were four units long and one wide, how many squares would it contain?
If it were five long and one wide? Six long? &c.
Rectangle 4 is how many units long?
How many wide?
How many squares does it contain?
How many squares in that part which is two units long, m n, and one unit wide, m l?
On account of the second unit in width, l k, how many times two squares are there?
If the width were one unit more, how many times two squares would there be?