Environmental Engineering Reference
In-Depth Information
4 Fractions, Decimals,
and Percent
Math is ubiquitous; it is invaluable to all aspects of life.
The number 10 divided by 2 gives an exact quotient of 5. This may be written 10/2
= 5. However, if we attempt to divide 7 by 9, we are unable to calculate an exact
quotient. This division may be written 7/9 (read “seven ninths”). The number 7/9
represents a number, but not a whole number, and is called a fraction. Simply put,
fractions are used to express a portion of a whole. The water/waterworks opera-
tor is often faced with routine situations that require thinking in fractions and, on
occasion, actually working with fractions. One of the common applications for the
rules governing the use of fractions in a math problem is dealing with various units
of measure. Units such as gallons per minute (gal/min, gpm) are actually fractions.
Another example is cubic feet per second (ft 3 /sec, cfs). As can be seen, understanding
fractions helps in solving a variety of problems.
A fraction is composed of three items: two numbers and a line. The number on
the top is the numerator , the number on the bottom is the denominator , and the line
in between them indicates division.
Numerator
Denominator
3
4
Division
The denominator indicates the number of equal-sized pieces into which the entire
entity has been cut, and the numerator indicates how many pieces we have.
FRACTIONS
In solving fractions, the following key points are important:
1. Fractions are used to express a portion of a whole.
2. A fraction consists of two numbers separated by a horizontal line or a diag-
onal line (for example, 1/6).
3. The bottom number, the denominator, indicates the number of equal-sized
pieces the whole entity has been cut into.
4. The top number, the numerator, indicates how many pieces we have.
5. Like all other math functions, how we deal with fractions is governed by
rules or principles.
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