A factory discharges 3000 L of wastewater daily. The treatment plant processes 70 % in a primary settler, 20 % in a secondary reactor, and the rest in a tertiary unit. How many litres are treated in the tertiary unit?
Answer
300 L
The correct answer is 300 L — Hence 300 L are treated in the tertiary unit.
Step-by-step solution
- Determine the remaining percentage: 100 % – (70 % + 20 %) = 10 %.
- Apply this percentage to the daily discharge: 3000 × 0.10 = 300 L.
- Hence 300 L are treated in the tertiary unit.
Common mistake: Adding percentages instead of subtracting from 100 %
Concept tested: Percentage calculations
Published · How this solution was prepared and checked
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