# Percent uncertainty

1. Jan 28, 2007

### future_vet

1. The problem statement, all variables and given/known data
What is the percent uncertainty in the area of a circle whose raduis is 1.8 x 10^4 cm?

2. Relevant equations
I calculated A=Pi x r^2 = 1017876020
After that, I am lost...

3. The attempt at a solution

Thanks!

Last edited: Jan 29, 2007
2. Jan 28, 2007

### future_vet

The thing is, I don't know what was used to measure the radius. Can I still know what the uncertainty is to calculate the %age?

Thanks!

3. Jan 28, 2007

### Staff: Mentor

If I'm not given any direct information about the uncertainty in the initial measurement (here, the radius), I take it to be +/- 1 in the last significant figure. In this case the uncertainty in the radius would be $0.1 \times 10^4$ cm.

4. Jan 28, 2007

### future_vet

Thanks a lot!

I calculated the percent uncertainty to be 5.6%. I think it is correct...

5. Jan 29, 2007