# Calculating volume of earth

1. Nov 27, 2009

### BogMonkey

I got this question on a multiple choice test and I couldn't do it. The question was
"Calculate the volume of the earth knowing that the mean radius is 6371 km."

What I did was multiply 4*pi*6371^3 then divided the answer by 3 but it didn't yield the correct answer. I got the solutions sheet for the test and heres how the teacher solved the problem

= 4pi * (6.371 * 10^3)^3 / 3
= 4pi * (6.371)^3 * 10^9 / 3

They're the first two steps of his solution but I'm completely lost. How do you magically get a different answer by using scientific notation? I know the laws of indices but I don't understand how I got a different answer because I didn't use scientific notation to represent 6371 km.

2. Nov 27, 2009

### Integral

Staff Emeritus
Since you have not shown us your final answer there is no way we can point you in the right direction. You are correct using scientific notation will not change the result.

3. Nov 27, 2009

### BogMonkey

1.08 * 10^15 m^3