Basic Mathematics for College Students

Sometimes more than one operation is needed to solve a problem involving

decimals.

352 Chapter 4 Decimals

Form The height (in millimeters) of a stack of 50 pennies, each of which is

1.55 thick, is the sum of fifty 1.55’s. This repeated addition can be calculated more

simply by multiplication.

is equal to times

 1.55  50

SolveUse vertical form to perform the multiplication:

StateA stack of 50 pennies is 77.5 millimeters tall.

CheckWe can estimate to check the result. If we use 2 millimeters to approximate

the thickness of one penny, then the height of a stack of 50 pennies is about

2 50 millimeters 100 millimeters. The result, 77.5 mm, seems reasonable.

1.55

 50

000

7750

77.50

The height of

stack of pennies

the number of

pennies in the stack.

the thickness

of one penny

The height of a

stack of pennies

EXAMPLE (^13) Weekly Earnings A cashier’s basic workweek is 40 hours.
After his daily shift is over, he can work overtime at a rate 1.5 times his regular rate
of $13.10 per hour. How much money will he earn in a week if he works 6 hours of
overtime?
Analyze

• A cashier’s basic workweek is 40 hours. Given


• His overtime pay rate is 1.5 times his regular rate of $13.10 per hour.Given


• How much money will he earn in a week if he works his regular shift
  and 6 hours overtime? Find
  Form To find the cashier’s overtime pay rate, we multiply 1.5 times his regular pay
  rate, $13.10.

The cashier’s overtime pay rate is $19.65 per hour.

We now translate the words of the problem to numbers and symbols.

13.10

 1.5

6550

13100

19.650

Self Check 13

WEEKLY EARNINGSA pharmacy

assistant’s basic workweek is

40 hours. After her daily shift

is over, she can work overtime

at a rate of 1.5 times her regular

rate of $15.90 per hour. How

much money will she earn in a

week if she works 4 hours of

overtime?

Now TryProblem 113

is equal to times plus times

 (^40)  $13.10  (^6)  $19.65
The total amount the
cashier earns in a week
his overtime
rate.
the number of
overtime hours
his regular
pay rate

40

hours

The total amount the

cashier earns in a week