3) Since there are 12 months in a year, there are four groups of 3 months in a year.
So, if 420 dollars are saved every three months, a total of
dollars will be saved per year.
4) Using the given figure, the difference between the two numbers is composed by two little squares. If this difference is 72, then one little square is 36.
The sum of the two numbers is composed by 8 little squares, for a total of
