The area of the square is 4 × 4 which equals 16cm^2. The area of a circle is π × radius^2, so using 3.14 as pi we can say that (3.14 × 16)/4 is the area of the quarter circle. This comes to 12.56, so added to 16 you get 28.56cm^2 as your answer, which can be rounded to 28.6cm^2. I hope this helps!
You cannot find the percent error of data without knowing the true length of the rope, as percent error is essentially a comparison between what you measured and what it actually is.
