Basic Mathematics for College Students

We can use multiplication to count objects arranged in patterns of neatly arranged
rows and columns called rectangular arrays.

1.4 Multiplying Whole Numbers 47

is equal to times

 18 8

Use vertical form to perform the multiplication:

In 2008, the average U.S. manufacturing worker earned $144 in an 8-hour workday.

1

6

8

 8

144



The amount earned in

an 8-hr workday

the rate per hour 8 hours.

The amount earned in

an 8-hr workday

The Language of Mathematics An arrayis an orderly arrangement. For

example, a jewelry store might display a beautiful arrayof gemstones.

EXAMPLE (^9) Pixels Refer to the
illustration at the right. Small dots of color,
called pixels, create the digital images seen on
computer screens. If a 14-inch screen has 640
pixels from side to side and 480 pixels from
top to bottom, how many pixels are displayed
on the screen?
Strategy We will multiply 640 by 480 to determine the number of pixels that are
displayed on the screen.
WHY The pixels form a rectangular array of 640 rows and 480 columns on the
screen. Multiplication can be used to count objects in a rectangular array.
Solution
We translate the words of the problem to numbers and symbols.
is equal to times

 640 480

To find the product of 640 and 480, we use vertical form to multiply 64 and 48 and
attach two zeros to that result.

Since the product of 64 and 48 is 3,072, the product of 64 0 and 48 0 is 307,2 00 .The
screen displays 307,200 pixels.

48

 64

192

2 880

3,072



The number of pixels

on the screen

the number of

pixels in a column.

the number of

pixels in a row

The number of pixels

on the screen

BR G B R G

G B R G B R

RG B RG

R G

R G B RG

G B R R

B

G B

R G

Pixel

Self Check 9

PIXELSIf a 17-inch computer

screen has 1,024 pixels from side

to side and 768 from top to

bottom, how many pixels are

displayed on the screen?

Now TryProblem 93