Basic Mathematics for College Students

40 Chapter 1 Whole Numbers

SECTION 1.4

Multiplying Whole Numbers

Objectives

1 Multiply whole numbers by

one-digit numbers.

2 Multiply whole numbers that

end with zeros.

3 Multiply whole numbers by

two- (or more) digit numbers.

4 Use properties of multiplication

to multiply whole numbers.

5 Estimate products of whole

numbers.

6 Solve application problems by

multiplying whole numbers.

7 Find the area of a rectangle.

Multiplication of whole numbers is used by everyone. For example, to double a recipe,

a cook multiplies the amount of each ingredient by two. To determine the floor space

of a dining room, a carpeting salesperson multiplies its length by its width. An

accountant multiplies the number of hours worked by the hourly pay rate to calculate

the weekly earnings of employees.

1 Multiply whole numbers by one-digit numbers.

In the following display, there are 4 rows, and each of the rows has 5 stars.

We can find the total number of stars in the display by adding: 5  5  5  5 20.

This problem can also be solved using a simpler process called multiplication.

Multiplication is repeated addition, and it is written using a multiplication symbol ,

which is read as “times.” Instead of adding four 5’s to get 20, we can multiply 4 and 5

to get 20.

Repeated addition Multiplication

5 + 5 + 5 + 5 = 4 5 = 20 Read as “4 times 5 equals (or is) 20.”

We can write multiplication problems in horizontalor vertical form.The numbers that

are being multiplied are called factors and the answer is called the product.

Horizontal form Vertical form

4  5  20

Factor Factor Product

A raised dot and parentheses ( )are also used to write multiplication in horizontal

form.



   Factor

Factor

 Product



5 

 4

20





5 stars in each row

4 rows

Symbols Used for Multiplication

Symbol Example

 times symbol 4  5

 raised dot 4  5

( ) parentheses (4)(5) or 4(5) or (4)5

To multiply whole numbers that are less than 10, we rely on our understanding of

basic multiplication facts. For example,

and

If you need to review the basic multiplication facts, they can be found in Appendix 1

at the back of the book.

2  3 6, 8(4)32, 9  7  63