- A90 min
- B80 min
- C70 min
- D60 min
Step-by-Step Solution
All three: L/min; 4,200 L takes 40 min. Then : 70 L/min; 2,100 L takes 30 min. Total 70 min. (60 min keeps R on throughout.)
Answer: C) 70 min
Three pumps feed a 6,300-litre tank at the rates shown in the figure. All three start together, and pump R is switched off when the tank is two-thirds full. How long does the filling take?
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