Question

Difficulty: HardRatios, Rates, and Percentages

A municipal utility operates three water desalination plants—Plant Alpha, Plant Beta, and Plant Gamma—to process seawater into purified drinking water. Each plant operates at a constant total intake rate of seawater and yields a specific percentage of brine byproduct, with the remainder converted to purified drinking water:

- Plant Alpha: Total intake rate of 40,00040,000 gallons per hour; 15%15\% of intake becomes brine byproduct.
- Plant Beta: Total intake rate of 60,00060,000 gallons per hour; 10%10\% of intake becomes brine byproduct.
- Plant Gamma: Total intake rate of 50,00050,000 gallons per hour; 20%20\% of intake becomes brine byproduct.

Match each operational metric on the left with its corresponding calculated value on the right.

  • The combined purified drinking water output rate of Plant Alpha and Plant Beta operating simultaneously (in thousands of gallons per hour).8888 thousand gallons per hour
  • The ratio of the total volume of brine byproduct produced by Plant Alpha in 55 hours to the total volume of brine byproduct produced by Plant Gamma in 44 hours.3:43 : 4
  • The total operational time (in hours) required for Plant Beta to produce the exact volume of purified drinking water that Plant Gamma produces in 99 hours.203\frac{20}{3} hours

Answer

The operational metrics match as follows: the combined output rate of Plant Alpha and Plant Beta is 8888 thousand gallons per hour; the ratio of brine byproduct volume produced by Plant Alpha (in 5 hours) to Plant Gamma (in 4 hours) is 3:43 : 4; and the time required for Plant Beta to equal Plant Gamma's 9-hour purified output is 203\frac{20}{3} hours.
Each calculation requires decomposing total plant intake into its constituent components (purified water and brine byproduct) using given percentages, followed by executing standard work-rate and ratio operations (R×T=WR \times T = W). The resulting values match 8888 thousand gallons per hour, 3:43 : 4, and 203\frac{20}{3} hours respectively.

Step-by-Step Solution

1
Calculate individual rates for purified drinking water and brine byproduct for each plant.
Plant Alpha: Purified = 0.85×40=340.85 \times 40 = 34 k gal/hr, Brine = 0.15×40=60.15 \times 40 = 6 k gal/hr. Plant Beta: Purified = 0.90×60=540.90 \times 60 = 54 k gal/hr, Brine = 0.10×60=60.10 \times 60 = 6 k gal/hr. Plant Gamma: Purified = 0.80×50=400.80 \times 50 = 40 k gal/hr, Brine = 0.20×50=100.20 \times 50 = 10 k gal/hr.
Deconstructing the total intake rates into purified water rates and byproduct rates allows direct substitution into each multi-part question.
2
Sum the purified drinking water rates of Plant Alpha and Plant Beta.
Combined purified rate = 34+54=8834 + 54 = 88 thousand gallons per hour.
When two plants operate simultaneously, their effective production rates add together.
3
Compute total brine output for Plant Alpha in 5 hours and Plant Gamma in 4 hours, then simplify the resulting ratio.
Alpha brine volume = 6×5=306 \times 5 = 30 thousand gallons. Gamma brine volume = 10×4=4010 \times 4 = 40 thousand gallons. Ratio = 30:40=3:430 : 40 = 3 : 4.
Total volume equals hourly rate multiplied by operational duration.
4
Find total purified output of Plant Gamma in 9 hours, and divide by Plant Beta's hourly purified rate.
Gamma purified total = 40×9=36040 \times 9 = 360 thousand gallons. Required time for Beta = 36054=203\frac{360}{54} = \frac{20}{3} hours.
Time equals total required volume divided by the rate of production.

Key Concept

Work rates and percent composition decomposition in multi-unit processing systems.
Estimated Time:2m 30s
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