percent error is [(abs(experimental - actual))/(actual)] * 100
(38.0 - 40.0 ) / 40.0 = 2.0 / 40 = 0.05
0.05 * 100 = 5
since there are 2 sigfigs, the answer is 5.0 %
I made the 2 positive since the absolute value of 38.0 - 40.0 was taken
There are only 2 sigfigs because of the subtraction of 38.0 - 40.0 gives 2.0, only 2 sigfigs