Question

Use differentials to estimate the amount of paint needed to apply a coat of paint 0.02 cm thick to a sphere with diameter 40 meters. (Recall that the volume of a sphere of radius r is V=(4/3)πr^3. Notice that you are given that dr=0.02.)

Answer 1

v = 4/3 πr^3
dv = 4πr^2 dr

so, plug in your numbers...

Answer 2

i did.
Dv=128pi. But the answer is 8pi/25

Answer 3

Check your units. Their answer is in m^3, since it is

4π(20^2)(.02/100)

Answer 4

how much paint is used to paint 500 rubber balls of radius 5 inches of the paint is 0.02 inches thick

Answer 5

my dv is comming as 0.24m^3 ,fir finding volume you can add this dv to actual volume considering radius as 20m