Pipes and Cisterns Model 1: Filling Together, and Filling Against a Drain

04 Try it yourself Interactive

One sign, five times the answer

Set the two times, then switch B between inlet and outlet and watch the last step move. The final step always checks the answer against the matching product rule, so you can see the shortcut and the unit method agree. Make the drain faster than the inlet and the solver stops and explains why there is no answer.

A fills in 20 min, B fills in 30 min

net +5 · 12 minutes

Set A to 30 and B to 20 as a drain. The drain is now the quicker pipe, so the tank loses ground every minute — and the product rule would hand you a confident negative.

Press Next to work through it one step at a time.

Tank units–

A per min–

B per min–

Time to fill–

step 0 / 0