If a flow control valve reduces flow from 120 gpm to 60 gpm with the same upstream pressure, what is the percent reduction in flow?

If a flow control valve reduces flow from 120 gpm to 60 gpm with the same upstream pressure, what is the percent reduction in flow?

• A. 25%
• B. 75%
• C. 50%
• D. 0%

Answer: (C)

When measuring how much a quantity decreases in percent, compare the drop to the original amount. percent reduction = (original - new) / original × 100%. Here the flow goes from 120 gpm to 60 gpm, a drop of 60 gpm. So (120 - 60) / 120 × 100% = 60 / 120 × 100% = 50%. Since the upstream pressure is the same, the change is entirely due to the flow decrease. A 50% reduction means the flow is halved; the other options would correspond to different amounts of drop (for example, a 25% reduction would be a 30 gpm drop, etc.).

When measuring how much a quantity decreases in percent, compare the drop to the original amount. percent reduction = (original - new) / original × 100%. Here the flow goes from 120 gpm to 60 gpm, a drop of 60 gpm. So (120 - 60) / 120 × 100% = 60 / 120 × 100% = 50%. Since the upstream pressure is the same, the change is entirely due to the flow decrease. A 50% reduction means the flow is halved; the other options would correspond to different amounts of drop (for example, a 25% reduction would be a 30 gpm drop, etc.).