EXAMPLE
Find the total calories in a meal consisting of a cheeseburger (550 calories),
French fries (352 calories), and a soft drink (110 calories).SOLUTION
Since you want to find the total number of items and the items are the same
(calories), you add: 550þ 352 þ 110 ¼ 1012 calories. Hence, the total
number of calories in the meal is 1012.SUBTRACTION
When you are asked to find the difference, i.e., ‘‘how much more,’’ ‘‘how
much less,’’ ‘‘how much larger,’’ ‘‘how much smaller,’’ etc., and the items are
the same, you subtract.EXAMPLE
The total area of Lake Superior is 81,000 square miles and the total area of
Lake Erie is 32,630 square miles. How much larger is Lake Superior?SOLUTION
Since you are asked how much larger is Lake Superior than Lake Erie, you
subtract. 81,00032,630¼48,370. Hence, Lake Superior is 48,370 square
miles larger than Lake Erie.MULTIPLICATION
When you are asked to find a total and the items are different, you multiply.EXAMPLE
An auditorium consists of 24 rows with 32 seats in each row. How many
people can the auditorium seat?SOLUTION
Since you want a total and the items are different (rows and seats), you
multiply:
32
24
128
64
768
The auditorium will seat 768 people.12 CHAPTER 1 Whole Numbers