A detail drawing shows a scale of 1/2" = 1'-0". If a dimension measures 3 inches on the drawing, what is the actual dimension?
Correct Answer
B) 6 feet
With a scale of 1/2" = 1'-0", each 1/2 inch on the drawing represents 1 foot actual. Therefore, 3 inches on the drawing equals 6 feet actual (3 ÷ 0.5 = 6).
Why This Is the Correct Answer
The scale 1/2" = 1'-0" means that every half inch on the drawing represents one actual foot. To find the actual dimension, we need to determine how many half-inch increments are in 3 inches (which is 6), and multiply by 1 foot each. This gives us 6 feet actual dimension.
Why the Other Options Are Wrong
Option A: 3 feet
This answer assumes a 1:1 ratio where 3 inches on the drawing equals 3 feet actual, but it ignores the scale factor completely.
Option C: 12 feet
This answer uses an incorrect scale conversion, possibly confusing it with a 1" = 4' scale or making an arithmetic error in the calculation.
Option D: 18 feet
This answer appears to multiply 3 inches by 6 instead of dividing by the scale factor, showing a fundamental misunderstanding of scale conversion.
Memory Technique
Remember 'Half and Double': when the drawing scale uses 1/2 inch, you double the drawing measurement to get the actual feet (3 inches × 2 = 6 feet).
Reference Hint
Look up architectural drawing scales and scale conversion in the construction documents section of your reference manual, typically found in the project management or blueprint reading chapters.
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