Page 364 - Basic College Mathematics with Early Integers

CHAPTER HIGHLIGHTS 341

Definitions and Concepts Examples

Section 4.1 Introduction to Decimals (continued)

TO ROUND A DECIMAL TO A PLACE VALUE TO THE RIGHT OF Round 86.1256 to the nearest hundredth.
THE DECIMAL POINT hundredths place
Step 1: Locate the digit to the right of the given place Step 1: 86.12 5 6
value. digit to the right
Step 2: If this digit is 5 or greater, add 1 to the digit in the
Step 2: Since the digit to the right is 5 or greater, we add 1
given place value and delete all digits to its right.
to the digit in the hundredths place and delete all
If this digit is less than 5, delete all digits to the
digits to its right.
right of the given place value.
86.1256 rounded to the nearest hundredth is 86.13.
Section 4.2 Adding and Subtracting Decimals

TO ADD OR SUBTRACT DECIMALS Add: 4.6 + 0.28 Subtract: 2.8 - 1.04
7 10
Step 1: Write the decimals so that the decimal points line 4.60 2.8 0
up vertically. + 0.28 - 1.04
Step 2: Add or subtract as with whole numbers. 4.88 1.76
Step 3: Place the decimal point in the sum or difference
so that it lines up vertically with the decimal
points in the problem.

Section 4.3 Multiplying Decimals and Circumference of a Circle

TO MULTIPLY DECIMALS Multiply: 1.48 * 5.9
Step 1: Multiply the decimals as though they are whole 1.4 8 ; 2 decimal places
numbers. * 5.9 ; 1 decimal place
Step 2: The decimal point in the product is placed so that 1 3 3 2
the number of decimal places in the product is 7 4 0 0
equal to the sum of the number of decimal places
8.7 3 2 ; 3 decimal places
in the factors.
The circumference of a circle is the distance around the circle. Find the exact circumference of a circle with radius
5 miles and an approximation by using 3.14 for .p
Radius C = pd or C = 2pr
C = 2pr
= 2p(5)
Diameter 22 5 miles
where p L 3.14 or p L . = 10p
7
L 10(3.14)
or
= 31.4
r The circumference is exactly 10p miles and approximately
31.4 miles.
d