Engineering drawing scales — when would an engineer’s scale be used? Select the scale expression that corresponds to the typical engineer’s (civil) scale used to read large-site drawings.

Introduction / Context:
Engineering drawings for civil and site plans commonly use “engineer’s scales,” which express distances as decimal feet (e.g., 1 inch on paper equals 10, 20, 30, 40, 50, or 100 feet in the field). In contrast, architectural scales use inches-to-feet in fractional form for buildings and interiors.

Given Data / Assumptions:

• Engineer’s (civil) scales: 1"=10', 1"=20', 1"=30', 1"=40', 1"=50', 1"=100'.
• Architectural scales: 1/4"=1'-0", 1/8"=1'-0", etc.

Concept / Approach:
Identify which listed scale is in decimal feet rather than architectural fractional feet. The option “1"=100'” means every inch on the drawing equals 100 feet in reality, a common civil scale for large sites and mapping where fine interior detail is unnecessary.

Step-by-Step Solution:

Verification / Alternative check:
Design standards and drafting textbooks list the standard engineer’s scale sets including 10, 20, 30, 40, 50, and 100 feet per inch.

Why Other Options Are Wrong:

• 1/4"=1'-0", 1/8"=1'-0", 3/4"=1'-0" are architectural scales.
• 1"=10 cm is metric and not a standard engineer’s (imperial) scale.

Common Pitfalls:

• Confusing a prime symbol (feet) and quote (inches); ensure units are consistent.

Final Answer:
1" = 100'