If 60 gallons per minute flow passes through a 1-1/2 inch pipe, what is the flow in gallons per minute through a 3 inch pipe?

If 60 gallons per minute flow passes through a 1-1/2 inch pipe, what is the flow in gallons per minute through a 3 inch pipe?

• A. 60 gal/min
• B. 120 gal/min
• C. 180 gal/min
• D. 240 gal/min

Answer: (D)

Flow rate depends on both velocity and cross-sectional area (Q = v × A). If the fluid keeps the same velocity in both pipes, the flow scales with the cross-sectional area. The diameter doubles from 1.5 inches to 3 inches, so the area increases by a factor of 4 (area ∝ d^2). Therefore the flow rate becomes 60 gal/min times 4, which is 240 gal/min.

Flow rate depends on both velocity and cross-sectional area (Q = v × A). If the fluid keeps the same velocity in both pipes, the flow scales with the cross-sectional area. The diameter doubles from 1.5 inches to 3 inches, so the area increases by a factor of 4 (area ∝ d^2). Therefore the flow rate becomes 60 gal/min times 4, which is 240 gal/min.