I find it easier to do the actual computation than to try to choose the correct answer from a bunch of alternatives.
You are given the area of a rectangle, as well as the length of one side. To find the length of the other side, you must divide the given side length into the area.
Thus, the unknown side length is
1.403E(-2) cm^2
----------------------- = 0.23E2 cm, or, better, 2.3E1, or 23 cm
6.1E(-4) cm
Now that you have this info, which of the given four steps do you judge to be appropriate and which inappropriate?
