A grading plan shows contour lines spaced 2 feet apart vertically. If the horizontal distance between two adjacent contour lines is 40 feet, what is the slope percentage?
Correct Answer
B) 5%
Slope percentage = (vertical rise ÷ horizontal run) × 100. Slope = (2 feet ÷ 40 feet) × 100 = 5%. This represents a relatively gentle slope suitable for most construction activities.
Why This Is the Correct Answer
Option B is correct because slope percentage is calculated using the formula (vertical rise ÷ horizontal run) × 100. With a vertical rise of 2 feet between contour lines and a horizontal distance of 40 feet, the calculation is (2 ÷ 40) × 100 = 5%. This represents the grade or steepness of the terrain between the two contour lines.
Why the Other Options Are Wrong
Option A: 2%
Option A (2%) incorrectly uses only the vertical rise without dividing by the horizontal run, or represents a calculation error in the slope formula.
Option C: 20%
Option C (20%) incorrectly reverses the calculation by dividing horizontal run by vertical rise (40 ÷ 2 = 20), which is the inverse of the correct slope formula.
Option D: 40%
Option D (40%) simply uses the horizontal distance value without applying the slope formula, ignoring the vertical rise component entirely.
Memory Technique
Remember 'RRH' - Rise over Run times Hundred. Also think 'small rise, big run = gentle slope' to check if your answer makes sense (5% is indeed a gentle slope).
Reference Hint
Look up 'Site Work and Grading' or 'Topographic Maps and Contour Lines' in your construction reference manual, typically found in the site preparation or surveying sections.
More Project Mgmt Questions
What is the minimum R-value required for wall insulation in Florida Climate Zone 2?
A subcontractor brings a new chemical product to your jobsite. Under the Globally Harmonized System (GHS), what information must be immediately available to workers?
A construction site has a trench that is 8 feet deep in Type B soil. What is the maximum allowable slope ratio for the trench walls without protective systems?
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?
What is the maximum recommended spacing between drywall screws when attaching to wood studs?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Previous Question
A mason is building a CMU wall and notices the blocks are absorbing water quickly from the mortar. What should be done before continuing?
Next Question
You are reviewing architectural plans that show a stairway with a 7.5-inch rise and 10-inch tread. A building official questions the design. What Florida Building Code requirement is likely being violated?