Differentials Problem

1. Jan 27, 2007

bodensee9

1. The problem statement, all variables and given/known data
Sorry, this may sound dumb, but How do I use differentials to estimate the amount of tin in a closed tin can with diameter 8 cm and height 12 cm if the tin is 0.04 cm thick?

2. Relevant equations
The volume of the can is V = pi*r^2h. So dV= 2*pi*rh*dr

3. The attempt at a solution

Could someone point out what I am doing wrong? I thought that since volume is pi*r^2h, and so dv = 2*pi*rhdr. So, wouldn't I just plug in 2*pi*4*12*0.04 to arrive at an estimate of the amount of the tin? Thanks so much!!

2. Jan 27, 2007

AngeloG

You are correct =).

V = pi * r^2 * h
dV = 2 * pi * h * r * dR
dV = 2 * pi * 12 * 4 * 0.04