[Guest]

A tank can be filled by pipe A in 30 minutes and by pipe B in 24 minutes. Outlet pipe C can empty the full tank in one hour and twenty minutes. If the tank is empty initially and if all the three pipes A, B and C are opened simultaneously, in how much time will the tank be full?

[Guest]

I believe it will be 16 minutes.

[Guest]

11 and 3/7 minutes, or about 11:26.

Method:

1/A + 1/B + 1/C = 1/Answer

[Guest]

11 and 3/7 minutes, or about 11:26.

Method:

1/A + 1/B + 1/C = 1/Answer

You wanna subtract 1/C don't you?

[Guest]

16 minutes.

[bonanova]

16 minutes.

Spoiler for solution:

A = 8 tanks / 240 minutes

B = 10 tanks / 240 minutes

C = -3 tanks / 240 minutes

In 240 minutes you get 8+10-3 = 15 tanks

In 16 minutes you get 1 tank

[Guest]

A tank can be filled by pipe A in 30 minutes and by pipe B in 24 minutes. Outlet pipe C can empty the full tank in one hour and twenty minutes. If the tank is empty initially and if all the three pipes A, B and C are opened simultaneously, in how much time will the tank be full?

never... unless you block the outlet pipe © - it won't fill

[Guest]

16 minutes

[Guest]

Artificial, W, Bonanova and Jenbali have got it. Good job. Extra kudos to Jenbali for your first post.

Rhapsodize, your method is correct, though C should be negative as it is an outlet pipe.

LIS, at the 16th min, the tank will be full. I am not sure who will be responsible to close the pipes at the right time, though.

[Guest]

LIS, at the 16th min, the tank will be full. I am not sure who will be responsible to close the pipes at the right time, though.

Yes i realized later that i read C as 20 min somehow? thought it was a catch question, came to me too late. What a thing to think about instead of cheering my son at football. - Wearing a footprint - ow!