Basic Mathematics for College Students

322 Chapter 4 Decimals

Success Tip Writing additional zeros after the last digit to the right of the

decimal point does not change the value of the decimal.Also, deleting

additional zeros after the last digit to the right of the decimal point does not

change the value of the decimal. For example,

54.954.9054.900 Because and in (^54 1009054) 1,000^900 simplest
form are equal to
These additional zeros do not
change the value of the decimal.
54 109.
5 Graph decimals on a number line.
Decimals can be shown by drawing points on a number line.
c.We are comparing two negative decimals. In this case, when two digits differ,
the decimal with the smaller digit is the greater number.
10.4 9
10.4 0 Write a zero after 5 to help in the comparison.
As we work from left to right, this is the first column in which the digits differ.
Since it follows that is greater than and we can write
10.41910.45.

1 5, 10.419 10.45

5

1

EXAMPLE (^6) Graph and 1.89 on a number line.
StrategyWe will locate the position of each decimal on the number line and draw
a bold dot.
WHYTo graph a numbermeans to make a drawing that represents the number.
SolutionThe graph of each negative decimal is to the left of 0 and the graph of
each positive decimal is to the right of 0. Since the graph of is
to the left of 1.23.

1.81.23, 1.8

1.8,1.23,0.3,

Self Check 6

Graph and 1.9

on a number line.

Now TryProblem 61

− 2 −101 2

1.1,1.64,0.8,

− 2 −101 2

−1.8−1.23 −0.3 1.89

6 Round decimals.

When we don’t need exact results, we can approximate decimal numbers by rounding.

To round the decimal part of a decimal number, we use a method similar to that used

to round whole numbers.

Rounding a Decimal

1. To round a decimal to a certain decimal place value, locate the rounding
   digitin that place.


2. Look at the test digitdirectly to the right of the rounding digit.


3. If the test digit is 5 or greater, round up by adding 1 to the rounding
   digit and dropping all the digits to its right. If the test digit is less than 5,
   round down by keeping the rounding digit and dropping all the digits to
   its right.