A duct has 3 sq ft of area and air velocity is 720 fpm. What airflow is carried?
Correct Answer
B) 2,160 cfm
Airflow is area x velocity = 3 sq ft x 720 fpm = 2,160 cfm.
Why This Is the Correct Answer
Airflow is area x velocity = 3 sq ft x 720 fpm = 2,160 cfm.
Why the Other Options Are Wrong
Option A: 720 cfm
duct airflow, choice a: 720 cfm is wrong because 720 cfm copies the air velocity as if it were airflow; the accepted calculation multiplies area by velocity.
Option C: 1,080 cfm
duct airflow, choice b: 1,080 cfm implies 1.5 sq ft at 720 fpm; the stated area is 3 sq ft, so.
Option D: 2,880 cfm
duct airflow, choice c: 2,880 cfm implies 4 sq ft at 720 fpm; the stated area is 3 sq ft, so.
Memory Technique
Store duct airflow with its last math move; nearby answers are usually unfinished versions of 2,160 cfm.
Reference Hint
Open Mechanical and Electrical Systems for Construction Managers, 4th Ed., 2024; use by topic index - HVAC capacity / airflow / air changes / TAB to confirm that Airflow is area x velocity = 3 sq ft x 720 fpm = 2,160 cfm.
More NASCLA Questions
Bid instructions require bid security with each sealed bid. Which purpose should the estimator associate with that requirement?
A wood deck surface has 320 sf of coverage. Boards have a 5-1/2 in. actual face width, and the order includes an 8 percent cutting allowance. What linear footage is closest?
Using the dimensions shown for the stabilized construction entrance, what is the plan area?
A reroof area requires 14,720 sf of rigid insulation. Boards are 4 ft by 8 ft, and the order includes 5 percent waste. How many boards are needed?
Two addenda revise the drawings before bid day. What must a responsive bidder normally do with those addenda?
A utility trench is 180 ft long, 3 ft wide, and 7 ft deep with vertical sides inside a trench shield. What excavation volume is required?
A 120 ft long Type C trench is cut with a 4 ft bottom width and a 6 ft depth. If side slopes are 1-1/2 horizontal to 1 vertical, what excavation volume is closest?
A storm pipe run needs 240 ft of bedding, 4 ft wide and 6 in. thick. Including a 10 percent ordering allowance, how many cubic yards of bedding aggregate are needed?
A mass excavation produces 1,180 loose cubic yards of material for off-site disposal. End-dump trucks can haul 18 loose cubic yards per trip. What truck count is required?
An asphalt-shingle roof has a slope of 3:12. Under the IBC low-slope asphalt-shingle provisions, what underlayment arrangement is required?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass