One pipe can fill the tank in 9 minutes while another pipe can empty completely filled tank in 90 minutes. If both the pipes are operated together on empty tank, how long (in minutes) will it take to fill the tank completely?
Given
Pipe A fills the tank in 9 minutes
rate tank/min.
Pipe B empties a full tank in 90 minutes
rate tank/min (emptying).
Both start together on an empty tank.
Formula Used
Net rate = filling rate - emptying rate
Time to fill
Solution
Net rate = tank/min.
Time to fill = minutes.
Alternate Method:
Assume tank capacity = LCM(9,90) = 90 units.
A fills 10 units/min; B empties 1 unit/min
net = 9 units/min.
Time = minutes.
English
100 Questions
100 Marks
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