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Area and volume: California D1 water distribution operator math

Pipe, tank, basin, trench and wall areas and volumes; force on a valve.

Below are 3 worked examples. Each answer is computed with the formulas and constants on the CA Exam Conversion Sheet (revised 4/30/2026), and the solution names the line it uses.

Formulas from the sheet for this topic

Example 1. A rectangular basin is 75 ft long and 51 ft wide, with water 19 ft deep. How many gallons does it hold?

  1. A) 544,000 gal
  2. B) 72,700 gal
  3. C) 28,600 gal
  4. D) 272,000 gal
Show the answer and worked solution

Answer: A) 544,000 gal

1. Rectangular Basin (Gal) = L × W × H × 7.48 [Sheet p.1, Area and Volume: "Rectangular Basin (Gal) = Length (Ft) x Width (Ft) x Height (Ft) x 7.48"]. 2. = 75 × 51 × 19 × 7.48 = 543,609 gal. 3. Answer: 544,000 gal (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Rectangular Basin (Gal) = Length (Ft) x Width (Ft) x Height (Ft) x 7.48"

Example 2. How many gallons does 1,900 ft of 20-inch water main hold?

  1. A) 31,000 gal
  2. B) 18,600 gal
  3. C) 15,500 gal
  4. D) 4,140 gal
Show the answer and worked solution

Answer: A) 31,000 gal

1. D = 20 ÷ 12 = 1.667 ft [12 in = 1 ft]. Keep (20 ÷ 12) in your calculator instead of the rounded value, so the answer is not thrown off. 2. Cylinder Volume (Gal) = .785 × D² × Length × 7.48 [Sheet p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"]. 3. = .785 × (20 ÷ 12)² × 1,900 × 7.48 = 30,990 gal. 4. Answer: 31,000 gal (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"

Example 3. How many gallons does 1,650 ft of 36-inch water main hold?

  1. A) 349,000 gal
  2. B) 87,200 gal
  3. C) 29,100 gal
  4. D) 11,700 gal
Show the answer and worked solution

Answer: B) 87,200 gal

1. D = 36 ÷ 12 = 3 ft [12 in = 1 ft]. 2. Cylinder Volume (Gal) = .785 × D² × Length × 7.48 [Sheet p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"]. 3. = .785 × (36 ÷ 12)² × 1,650 × 7.48 = 87,196 gal. 4. Answer: 87,200 gal (rounded to 3 significant figures).

Source: CA Exam Conversion Sheet (Revised 4/30/2026), p.1, Area and Volume: "Cylinder Volume (Gal) = .785 x D2 x Height or Length (Ft) x 7.48"

Want it on paper? Free printable D1 water distribution math worksheet with answer key.

Practice all 124 area and volume problems for CA D1 Math

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