The material in Chapter 3 describes aspects related to using water in wildland firefighting. These concepts include determining the weight of water, a description of factors related to friction loss, a review of basic drafting guidelines, as well as calculations related to volume, pump pressure, and flow rate. The chapter also provides instructions for estimating different parameters in the field, as well as a round-off table for ease of use.

UNIT CONVERSION AND CONVERSION FACTORS

A unit conversion expresses the same property as a different unit of measurement. For instance, time can be expressed in minutes instead of hours, while distance can be converted from miles to kilometers, or feet, or any other measure of length. Often measurements are given in one set of units, such as feet, but are needed in different units, such as chains. A conversion factor is a numeric expression that enables feet to be changed to chains as an equal exchange. 

INTRODUCTION

Chapter 2 provides information about converting units of measure, using known relationships called conversion factors. 

In completing this chapter, you'll learn how to set up a unit cancellation table and complete common unit conversion operations. The chapter also contains tables of typical units used by the wildland fire community.

RATIOS

A ratio is a proportional relationship of one value to another, e.g., the ratio of gas to oil in chain saw mix. Ratios can be written either as a fraction, 1/2, or in ratio notation, 1:2. The value of a ratio is the division of the first number by the second number. For example, consider the ratio 1:40 . This ratio is read as "1 to 40". Any fraction, for instance, 1/20, can also be written as a ratio: 1:20

SUBTRACTING FRACTIONS

Similar to adding fractions, fractions must have a common denominator (the bottom numbers must be the same) before being subtracted.

There are three steps to subtracting fractions:

ADDING FRACTIONS

There are three steps to adding fractions:

DIVIDING FRACTIONS

Division of fractions involves using the reciprocal (flipped form) of the second fraction. The reciprocal of a number is such that the product of a number and its reciprocal is 1.

MULTIPLYING FRACTIONS

A whole number and a fraction, or two or more fractions, can be multiplied together. Whole numbers and fractions must be changed to all fractions, with no whole numbers, in order to multiply.

There are three steps to multiplying fractions:

SIMPLIFYING FRACTIONS

Simplifying a fraction is writing a number in its most basic form. Sometimes fractions involve very large numbers in both the numerator (top number) and in the denominator (bottom number). As a general rule, it is easier to work with simpler fractions. So, always simplify.

There are three basic rules for simplifying fractions:

FRACTIONS: BITS AND PIECES

Fractions are used often, for instance when adding leftover pails of foam or mixing gas and oil for chain saw fuel.