Download sxpe-xemmh R36-R44

sxpe-xemmh R36-R44
11/22/05
4:31 PM
MAZER
Page 41
Fractions
a
A fraction is a number in the form , where b is not equal to 0. A fraction
b
is in simplest form if its numerator and denominator have a greatest
common factor (GCF) of 1. To simplify a fraction, divide its numerator
and denominator by their GCF.
Example
A caterpillar is 40 millimeters long. The head of the caterpillar is 6 millimeters long. To
compare the length of the caterpillar’s head with the caterpillar’s total length, you can
write and simplify a fraction that expresses the ratio of the two lengths.
Len gth of head
6 mm
Write the ratio of the two lengths: Total length = 40 mm
Write numerator and denominator
as products of numbers and the GCF:
32
= 20 2
Divide numerator and
denominator by the GCF:
32
= 20 2
1
3
= 20
1
Simplify:
3
ANSWER In simplest form, the ratio of the lengths is .
20
MATH HANDBOOK
Percents
A percent is a ratio that compares a number to 100. The word percent means
“per hundred” or “out of 100.” The symbol for percent is %.
For instance, suppose 43 out of 100 caterpillars are female. You can represent
this ratio as a percent, a decimal, or a fraction.
Percent
Decimal
43%
0.43
Fraction
43
100
Example
In the preceding example, the ratio of the length of the caterpillar’s head to the caterpil3
lar’s total length is 2
0 . To write this ratio as a percent, write an equivalent fraction that
has a denominator of 100.
Multiply numerator and 3
35
denominator by 5: 20 = 20 5
15
= 100
Write as a percent:
= 15%
ANSWER The caterpillar’s head represents 15 percent of its total length.
Math Handbook R41
PDF