CSLB C-20 HVAC ContractorPlanning and LayoutEasy
A technician is reading a mechanical blueprint drawn at a scale of 1/4 inch = 1 foot. A duct run measures 2 inches on the drawing. What is the actual length of the duct run in the field?
- A8 feet
- B4 feet
- C16 feet
- D24 feet
Show answer & explanationAnswer & explanation
Correct answer: A. 8 feet
At a scale of 1/4 inch = 1 foot, each 1/4 inch on paper equals 1 actual foot. Two inches contains eight 1/4-inch segments (2 ÷ 0.25 = 8), so the actual length is 8 feet.
Why the other options are wrong
- B. This would result from dividing by the wrong scale factor.
- C. This doubles the correct answer, a common scale-reading error.
- D. This assumes an incorrect 1/8 inch scale factor.
Blueprint Scale Reading
A blueprint scale converts a measured distance on paper into an actual field dimension using a fixed ratio.
- 1/4"=1' means each 1/4 inch equals 1 actual foot
- Divide drawing measurement by scale factor to get real length
- Architect's scale rulers simplify this conversion
Memory trick: Quarter inch, whole foot — measure small, build big.