===================================================
Work Shown:
Subtract the values to get 2.1-1.5 = 0.6
Brianna is off by 0.6 liters
Divide that error by the true value 1.5 to get 0.6/1.5 = 0.40
Then move the decimal point 2 spots to the right to arrive at 40%
Therefore, the percent error is 40%
------------------
The formula you can apply is:
[tex]P = \frac{|G-T|}{T}*100\%[/tex]
where
P = percent error
G = guess value (in this case it is 2.1)
T = true value (which is 1.5 in this case)
If we were to apply the formula, then we get:
[tex]P = \frac{|G-T|}{T}*100\%\\\\P = \frac{|2.1-1.5|}{1.5}*100\%\\\\P = \frac{|0.6|}{1.5}*100\%\\\\P = \frac{0.6}{1.5}*100\%\\\\P = 0.40*100\%\\\\P = 40\%\\\\[/tex]