Fractions, Decimals, and Percent - Basic Mathematics for Water and Wastewater Operators - page 102

■ Example 4.6
Problem: Biosolids contain 5.8% solids. What is the concentration of solids in deci-
mal percent?

Solution:

Percent
100

58
100

.

Decimalpercent = = = 0 058 .

Note: Unless otherwise noted, all calculations in the text using percent values
require the percent to be converted to a decimal before use.

To determine what quantity a percent equals, first convert the percent to a decimal
and then multiply by the total quantity:

Quantity = Total × Decimal percent (4.2)

■ Example 4.7
Problem: Biosolids drawn from the settling tank are 5% solids. If 2800 gal of biosol-
ids are withdrawn, how many gallons of solids are removed?

Solution:

5
100

× 2800 gal = 140 gal

■ Example 4.8
Problem: Convert 0.55 to percent.

Solution:

55
100

055 . =×= 100 55 %

(To convert 0.55 to 55%, we multiply by 100, or simply move the decimal point two
places to the right.)

■ Example 4.9
Problem: Convert 7/22 to a decimal percent to a percent.

Solution:

7
22

= 0 318 . ; 0 318 . × 100 = 31 8 . %