# word problem calculus

• October 26th 2009, 04:21 PM
kashifzaidi
word problem calculus
An upright cylindrical tank with radius 7 m is being filled with water at a rate of 4 m3/min. How fast is the height of the water increasing? (Round the answer to four decimal places.)

A = pi * r^2 = 49 pi

(4 m^3 / min) / 49 pi m^2
= .2565 m / min

Can you plz help me with this and correct me because it may not be correct answer.

Thanks
• October 26th 2009, 04:28 PM
Jameson
You have the right answer but the setup looks very wrong to me.

You should start with $V=\pi r^2 h$ . r is constant so $V=49 \pi h$. Now take the derivative in terms of t. This leads to the same answer you got, but I don't know if you get the reason why it's this answer. Do you?
• October 26th 2009, 04:47 PM
kashifzaidi
actually this is from online HW and the computer doesnt accept my answer.