Basic Units of Measurement and Conversions - Basic Mathematics for Water and Wastewater Operators - page 51

■ Example 2.109
Consider the height of the Washington Monument. We may write it as 169,000 mm,
16,900 cm, 169 m, or 0.169 km, using the units of millimeter (prefix “milli,” symbol
“m”), centimeter (prefix “centi,” symbol “c”), or kilometer (prefix “kilo,” symbol “k”).
C onversion if aCtor t aBles
Conversion factors are given alphabetically in Table 2.6 and are listed by unit cat-
egory in Table 2.7.
■ Example 2.110
Problem : Find degrees in Celsius of water at 72°F.
Solution:
°C = 5/9 × (°F - 32) = 5/9 × (72 - 32) = 22.2
W ater /W asteWater C onversion e xaMples
■ Example 2.111
Convert cubic feet to gallons.
Gallons (gal) = Cubic feet (ft 3 ) × 7.48 (gal) l /f (ft3) 3
Problem: How many gallons of biosolids can be pumped to a digester that has 3800 ft 3
of volume available?
Solution:
Gallons = 3800 ft 3 × 7.48 gal l /f ft3 3 = 28,424 gal
■ Example 2.112
Convert gallons to cubic feet.
Cubic feet (ft 3 ) = Gallons ÷ 7.48 gal/ft 3
DID YOU KNOW?
Units and dimensions are not the same concepts. Dimensions are concepts
such as time, mass, length, or weight. Units are specific cases of dimensions,
such as hour, gram, meter, or pound. You can multiply and divide quantities
with different units: 4 ft × 8 lb = 32 ft-lb, but you can add and subtract terms
only if they have the same units. So, 5 lb + 8 kg = no way!