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Math practice questions

35 questions from the plumbing fundamentals practice test.

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Math practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

What this covers

Sample questions

A column of water about how tall produces a pressure of 1 psi at its base?

  1. 0.433 ft
  2. 27.7 ft
  3. 34 ft
  4. 2.31 ft
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D. 2.31 ft

Each foot of water gives 0.433 psi, so 1 psi takes 1 / 0.433 = 2.31 ft. 0.433 is the psi per foot, not feet per psi. 27.7 is the number of inches (not feet) of water column in 1 psi, and 34 ft is roughly the head equal to atmospheric pressure.

Reference: Hydrostatics: 0.433 psi per foot of head

Compared with a 2 in. pipe, the cross-sectional area of a 4 in. pipe of the same type is about how many times as large?

  1. 2 times
  2. 8 times
  3. 4 times
  4. 16 times
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C. 4 times

Area depends on the square of the diameter. Doubling the diameter gives 2 x 2 = 4 times the area. Choosing 2 times treats area as if it grew directly with diameter.

Reference: Geometry: area of a circle, A = 0.7854 x d squared

A horizontal drain 30 ft long is graded at 1/8 in. per foot. What is the total fall?

  1. 3-3/4 in.
  2. 2-1/2 in.
  3. 7-1/2 in.
  4. 3 in.
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A. 3-3/4 in.

30 ft x 1/8 in. per ft = 30/8 = 3-3/4 in. 7-1/2 in. is the fall at 1/4 in. per foot, and 2-1/2 in. comes from dividing 30 by 12.

Reference: Plumbing math: fall = length x grade

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