AIT Mathematics for Trades 3 β Questions and Answers
Question 1: An electrician needs to run conduit at a 30Β° angle. If the horizontal run is 10 feet, what is the approximate length of conduit needed? (sin 30Β° = 0.5, cos 30Β° β 0.866)
- 11.55 ft (Correct answer)
- 8.66 ft
- 5 ft
- 20 ft
Correct answer: 11.55 ft
Conduit length = horizontal run / cos 30Β° = 10 / 0.866 β 11.55 ft.
Question 2: A welder needs to fill a cylindrical tank with a radius of 3 ft and a height of 5 ft. What is the volume? (Ο β 3.14)
- 141.3 cu ft (Correct answer)
- 47.1 cu ft
- 94.2 cu ft
- 282.6 cu ft
Correct answer: 141.3 cu ft
V = Ο Γ rΒ² Γ h = 3.14 Γ 9 Γ 5 = 141.3 cu ft.
Question 3: Bolt holes on a flange are spaced equally. If 8 holes are placed on a 12-inch diameter bolt circle, what is the center-to-center arc spacing in inches? (Ο β 3.14)
- 4.71 in (Correct answer)
- 1.5 in
- 9.42 in
- 3.14 in
Correct answer: 4.71 in
Circumference = Ο Γ 12 = 37.68 in; spacing = 37.68 / 8 = 4.71 in.
Question 4: A piece of steel bar stock weighs 3.5 lbs per foot. An apprentice needs 7 pieces each 2.5 feet long. What is the total weight?
- 61.25 lbs (Correct answer)
- 87.5 lbs
- 24.5 lbs
- 43.75 lbs
Correct answer: 61.25 lbs
Total length = 7 Γ 2.5 = 17.5 ft; weight = 17.5 Γ 3.5 = 61.25 lbs.
Question 5: A roof has a 6:12 pitch (rise:run). If the horizontal run is 18 feet, what is the total rise?
- 9 ft (Correct answer)
- 12 ft
- 3 ft
- 6 ft
Correct answer: 9 ft
Pitch 6:12 means 6 inches rise per 12 inches run; 6/12 Γ 18 ft = 9 ft rise.
Question 6: A plumber orders pipe in 20-foot lengths. If a job requires 6 pieces at 3'8" each, how many full 20-foot lengths must be purchased?
- 2 (Correct answer)
- 3
- 4
- 1
Correct answer: 2
Each piece = 3 ft 8 in = 44 in = 3.667 ft; total = 6 Γ 3.667 = 22 ft; 2 lengths of 20 ft = 40 ft, which covers 22 ft β wait, 22 ft > 20 ft so 2 lengths needed.
Question 7: A motor runs at 1,750 RPM and is connected via belt to a pulley with a 6-inch diameter. If the driven pulley has a 10-inch diameter, what is the driven speed?
- 1,050 RPM (Correct answer)
- 2,917 RPM
- 750 RPM
- 1,750 RPM
Correct answer: 1,050 RPM
Driven RPM = (driver diameter / driven diameter) Γ driver RPM = (6/10) Γ 1,750 = 1,050 RPM.
AIT Mathematics for Trades 3
An electrician needs to run conduit at a 30Β° angle.
If the horizontal run is 10 feet, what is the approximate length of conduit needed? (sin 30Β° = 0.5, cos 30Β° β 0.866)