The difference between an observational study and an experiment is thatin an observational study only one group is studied, and in an experiment two groups are studied in an observational study, researchers do not control treatment, and in an experiment they doin an experiment cause and effect is analyzed, and in an observational study, it is not in an experiment one group is studied over a short period of time, and in an observational study, the group is studied over a longer period of time

In an observational study, researchers do not control treatment, and in an experiment they do .

Step-by-step explanation:

Observational study is the study where the researcher observes the subjects and measures variables, but does not influence the population where as in an experiment the experimenter has control on the independent variable to see the effect on the dependent variable.

So the correct difference between an observational study and an experiment is that "in an observational study, researchers do not control treatment, and in an experiment they do."

Well, what I would do [not sure if it's the correct way], is use the white area as a sector of a circle. The top right of the box is the center of the circle, so the radius is 6.
Then, by the white portion being one quarter of the circle (90° out of 360°), I could calculate the that pink shaded region = the total square (6×6) minus the white sector.
So area (A) of white sector (s): A(s) = 1/4×pi×r^2

36 - 28.27 = 7.73