LEAVING CERT ORDINARY MATHS - cannot figure it out..

blomkvist

Need help with this, please.

"Oil flows through a circular pipeline of radius 4cm at the rate of 20cm/second.
How long will it take to fill a cylindrical tank of diameter 1.2 metres and height 3 metres?

Give your answer in minutes.


volume of cylinder = pi r squared h

Bucklesman

blomkvist wrote: »

Need help with this, please.

"Oil flows through a circular pipeline of radius 4cm at the rate of 20cm/second.
How long will it take to fill a cylindrical tank of diameter 1.2 metres and height 3 metres?

Give your answer in minutes.


volume of cylinder = pi r squared h

Another way of putting it would be that the volume of a cylinder of radius 4cm and height 20cm in oil is added to the tank every second.

Find the volume of the tank and divide it by the volume added per second.

blomkvist

Ya that is basically whats in the book, and i have just done another one like it but i just cannot get the right answer to this one. the answer is 56 and 1/4.

Melia

The volume added per second is:

pi*r^2*h = pi*(0.04m)^2*(0.20m) = 0.00032*pi cubic metres per second

The volume of the tank is:

pi*r^2*h = pi*(1.2m/2)^2*(3m) = 1.08*pi cubic metres

So to get the time it takes to fill the tank, divide 1.08*pi cubic metres by 0.00032*pi cubic metres per second, and you get 3375 seconds, or 56.25 minutes.

blomkvist

Thank you very much for the help!!!

Melia

No problem - did you figure out where you were going wrong?

blomkvist

ya it was when changing the 4cm to metres and the 20 cm . But i understand it now, thanks again