Basic Math Operations - Mathematics and Statistics for the Environment - page 52

■ EXAMPLE 2.29
Problem: Solve for the unknown value x in the problem given below.

34
2

. = 6

x

Solution:

34 . ×=× 26

26
34

x

×

x = = 353 .

.

■ EXAMPLE 2.30
Problem: 1 lb of chlorine is dissolved in 65 gal of water. To maintain the same concentration, how
many pounds of chlorine would have to be dissolved in 150 gal of water?

Solution:

1lb
gal

lb
150 gal

x

=

65

65 ×=× x 1 150

1 × 150

65

x = = 2 .. 3lb

■ EXAMPLE 2.31
Problem: It takes 5 workers 50 hr to complete a job. At the same rate, how many hours would it take
8 workers to complete the job?

Solution:

5workers
8workers

hr
50 hr

x

=

550
8

×

x = = 31.3 hr

■ EXAMPLE 2.32
Problem: If 1.6 L of activated sludge (biosolids) with volatile suspended solids (VSS) of 1900 mg/L
are mixed with 7.2 L of raw domestic wastewater with BOD of 250 g/L, what is the food/microor-
ganisms (F/M) ratio?

Solution:

F
M

Amount of BOD
Amount of VSS

250 mg/L × 7.2 L 059

1

.

= = = = 059 .

1900 mg/L × 1.6 L