A detail drawing shows a scale of 3/4" = 1'-0". If a dimension measures 2.25 inches on the drawing, what is the actual dimension?
Correct Answer
B) 3'-0"
At 3/4" = 1'-0" scale, each 3/4 inch represents 1 foot. 2.25 ÷ 0.75 = 3, so the actual dimension is 3'-0".
Why This Is the Correct Answer
To solve this scale conversion problem, we need to determine how many scale units fit into the measured dimension. The scale 3/4" = 1'-0" means that every 3/4 inch on the drawing represents 1 foot in reality. By dividing the measured dimension (2.25 inches) by the scale factor (0.75 inches), we get 3, which means the actual dimension is 3 feet or 3'-0".
Why the Other Options Are Wrong
Option A: 2'-6"
This answer results from incorrectly calculating 2.25 ÷ 0.75 = 2.5 feet instead of 3 feet, or from misunderstanding the scale relationship.
Option C: 3'-6"
This answer suggests the calculation yielded 3.5 feet, which would occur if someone incorrectly added 0.5 feet to the correct answer or made an error in the division.
Option D: 4'-0"
This answer would result from incorrectly calculating the scale conversion, possibly by multiplying instead of dividing, or by misinterpreting the scale ratio.
Memory Technique
Remember 'Drawing ÷ Scale = Real' - always divide the drawing measurement by the scale factor to get the real-world dimension.
Reference Hint
Construction drawings and specifications chapter, architectural drafting standards section
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