Technical Standards and Safety Authority (TSSA) G3 Practice Exam

If the scale on a mechanical drawing is 1/8"- 1'0", then a line measuring 4" is actually how long?

1. 32 inches

2. 4 feet

3. 8 feet

4. 32 feet

The correct answer is: 32 feet

To determine the actual length represented by a line measuring 4" on a mechanical drawing with a scale of 1/8"-1'0", it's important to understand how the scale works. The scale indicates that every 1/8 inch on the drawing corresponds to 1 foot in reality. First, we convert the length on the drawing into how many eighths of an inch it contains. A 4" line is equivalent to 32 eighths of an inch because there are 8 eighths in 1 inch: 4 inches × 8 eighths/inch = 32 eighths. Given the scale of 1/8"-1'0", each of those 32 eighths represents 1 foot in reality. Therefore, since there are 32 eighths, the actual length can be calculated as: 32 eighths × 1 foot/eighth = 32 feet. This clarifies that a line measuring 4" on the drawing indeed corresponds to a real-world length of 32 feet.