Thread: related rates help

The Question is:
Water drains from the conical tank shown in the figure at the rate of 5ft^3/min.
How fast is the water level dropping from when h=6ft?

ok the relation between the variables h and r is: 5r/2=h

And i know the answer to the question is .276 ft/min, but i don't know how you get that.

What i did was do the derivative of the cone volume formula: (1/3)pi(r^2)h using the product rule and i differentiate the h as well. Plus i even substitute r with 2h/5 (since i want to know r in terms of h) after that i replace everything with the appropriate numbers and my answer is different. Can you guys show me how to do this step by step? Thank you.

EDIT: there is an upside down cone with a base radius of 4in and height of 10 in and there is an r and h which represents the height of the water and the base radius of it as well. Also the question before that says: What is the relation between the variables h and r? And that is every part of the question.

PLease, post all the information you were given, in order to help you better.

Originally Posted by maximade

The Question is:
Water drains from the conical tank shown in the figure at the rate of 5ft^3/min.
How fast is the water level dropping from when h=6ft?

ok the relation between the variables h and r is: 5r/2=h

And i know the answer to the question is .276 ft/min, but i don't know how you get that.

What i did was do the derivative of the cone volume formula: (1/3)pi(r^2)h using the product rule and i differentiate the h as well. Plus i even substitute r with 2h/5 (since i want to know r in terms of h) after that i replace everything with the appropriate numbers and my answer is different. Can you guys show me how to do this step by step? Thank you.

since ,





you know ... take the time derivative of the above equation and determine when