The percentage error in the calculated area of the square is 4.04%.
This is calculated by taking the difference between the actual area and the measured area, and then expressing it as a percentage of the actual area.
In this case, the actual area is 100cm x 100cm = 10000 cm2 and the measured area is 102cm x 102cm = 10404 cm2
The difference (10404 - 10000) = 404 cm2 which is 4.04% of the actual area.