Posted by Hannah on .
I am trying to calculate my percent error for an experiment conducted. I need to compare my average density calculated to the accepted average density but I am having trouble doing this because of the conversions.
My average density was 0.12 g/mm^3. The accepted value is for iron which is 7.8 X 10^3 kg/m^3.
So to get 0.12 g to kg I multiplied by 1000 and got 120.
Then I subtracted 120 from 7.80 X 10^3.
Is this correct so far??

Math(Please help, thank you) 
Steve,
You got it backwards:
0.12kg is 120g
0.12g = 0.00012kg
.12g * 1kg/1000g = .00012kg 
Math(Please help, thank you) 
Steve,
Oops. Forgot to include the volume:
.12g/mm^3 * 1kg/1000g * 1m^3/(1000mm)^3 = 120000kg/m^3 
Math(Please help, thank you) 
Hannah,
Oh ok so now to find the percent error do I subtract 120,000 from 7800 and then multiply by 100?

Math(Please help, thank you) 
Steve,
well, if the correct value is 10, and you get 12, then the percent error is (1210)/10 * 100 = 20%
Yours is figured the same way, but the values are so different, I wonder whether there is something wrong here. 
Math(Please help, thank you) 
Hannah,
Yes my data is probably wrong I'm just not sure where I messed up