I think I'm making this problem way too complicated than it really is.

[bearhug]

Assuming that 71% of the Earth’s surface is covered with water at an average depth of 2.1 mi, estimate the mass of the water on the Earth in kilograms.

What I originally did for this problem was find the total surface area of the Earth to be 1.97e8 mi^2 and multiplied by 0.71 to get the water's surface area to be 1.40e8mi^2. Then I multiplied that to 2.1 mi to get volume and found mass using D= m/V and converting to kg. The answer I got was 1.22e15 kg and it's wrong. (This is done on a computer program). I'm not sure if my math is wrong or if I'm making it a lot more complicated than it really is.

Any help would be appreciated

 

[berkeman]

Looks like the correct approach to me. What did you use to get the surface area of the earth? You are mixing units in your explanation of your work -- did you use the correct conversion factors? Maybe post a more complete listing of your work, and we can see if anything pops out at us.


EDIT -- not really "mixing" units...I misspoke. Maybe it's an error in the mass/Volume part?

 

[chroot]

You seem to have the correct approach, but perhaps you made an arithmetic or unit conversion error. I get this:

Surface area of Earth: 5.1 × 10¹⁴ m²
Volume of oceans: 1.2 × 10¹⁸ m³
Mass of oceans: 1.2 × 10²¹ kilograms

- Warren

 

[bearhug]

After looking at all replies I checked my math again and got what chroot got, 1.2x10^21 kg thanks for the help, at least I know that I understand the problem.