Fractions, Decimals, and Percent - Basic Mathematics for Water and Wastewater Operators - page 98

12. Multiplying fractions: In order to multiply fractions, simply multiply the
numerators and denominators together, and reduce to the simplest terms.
For example, find the result of multiplying 1/8 × 2/3:

1
8

×= ×

2
3

12
83

2
24

1
12 × ==

13. Dividing fractions: To divide fractions, simply invert the denominator (turn
it upside down), multiply, and reduce to simplest terms; for example, to
divide 1/9 by 2/3:

1
9
2
3

1
9

3
2

13
92

×
× ==

3
18

1
6

=×=

Note: The divide symbol can be “÷” or “/” or “—.”

14. Fractions to decimals: To convert a fraction to a decimal, simply divide the
numerator by the denominator; for example,

1/2 = 0.5, 5/8 = 0.625, 7/16 = 0.4375, 1/4 = 0.25

15. Change inches to feet: To change inches to feet divide the number of inches
by 12; for example,

5/12 = 0.42 feet

■ Example 4.2
Problem : Change the following to feet: 2 inches, 3 inches, 4 inches, 8 inches.

Solution:
2/12 = 0.167 feet
3/12 = 0.25 feet
4/12 = 0.33 feet
8/12 = 0.667 feet

DECIMALS

Although we often use fractions when measuring things, dealing with decimals can
be easier when we perform calculations, especially when working with pocket calcu-
lators. A decimal is composed of two sets of numbers. The numbers to the left of the
decimal are whole numbers, and the numbers to the right of the decimal are parts of
a whole number (a fraction of a number), as shown below: