# Homework Help: Square pyramid:

1. Nov 26, 2007

### momo89

An underground oil storage tank ABCDEFGH is part of an inverted square pyarmid, as shown in the diagram. the complete pyramid has asquare base of side 12 m and height 18 m.the depth of the tank is 12 m.

http://haniny.com/haniny/Square_pyramid.gif

when the depth of oil in the tank is h meters,show that the volume vm^3 is given by

V=4/27(h+6)^3 -32

oil is being added to the tank at the constant rate of 4.5m^3 s^-1 at the moment when the depth of oil is 8 m.Find the rate at which the depth is increasing

2. Nov 26, 2007

### HallsofIvy

First this has absolutely nothing to do with differential equations!

Second, it looks to me like homework so I am going to move this to the "homework: Calculus and Beyond" section.

Finally, you must show some attempt to do the problem yourself so that we can see what kind of help you need.

3. Nov 26, 2007

### HallsofIvy

What is the difference between the "height" of the pyramid and the "depth" of the tank?

4. Nov 26, 2007

### momo89

i do not know:uhh:

i need the solution for the question!!!

5. Nov 26, 2007

### momo89

6. Nov 26, 2007

### VietDao29

So... that mean, you don't need help? What you need is a complete solution, eh? :grumpy: :grumpy: :grumpy:

Do you find it a little bit unfair for us all just to just sit, and solve the problems for you?!?! No, we are not paid to do that!!! We are here to help you, and not to feed you with complete solutions.

Now, take some time off to read the sticky on top of this forum please:

The new version can be found https://www.physicsforums.com/showthread.php?t=94383".

Then, please collaborate. Show some work!!!

Last edited by a moderator: Apr 23, 2017
7. Nov 26, 2007

### momo89

thank you very much

Last edited by a moderator: Apr 23, 2017
8. Nov 26, 2007

### HallsofIvy

You apparently are unable to even state the problem correctly. You said "the height of the pyramid is 18 m" and "the depth of the tank is 12 m" but do not know what those mean. I strongly suspect that the "6" in "(h+6)" comes from the difference between the height of the pyramid and the depth of the tank, but I can't be sure when I don't know what they correspond to on your picture.

Oh, and when you say "i do not think so" to my statement that this problem has nothing to do with differential equations. If you believe it does, I would like to see what kind of differential equation is involved!

Last edited by a moderator: Nov 27, 2007
9. Dec 5, 2007

### PatPwnt

Couldn't you make a differential equation because the rate at which the depth increases decreases as the depth goes up? The volume is increasing at a constant rate. The depth is not.