Answer all the questions below and press submit to see how many you got right.
Area : The amount of unit squares that is needed to cover a 2-dimensional shape.
Centimeter : A centimeter ($cm$) is $\frac{1}{100}$ of a meter.
Circle : A circle is a two-dimensional shape. The boundary of a circle is a set of points that has the same distance (the radius) from the center of the circle.
Pi : Pi or $\pi$ is an irrational number approximately equal to 3.14 that is defined as the quotient of the circumference and the diameter of a circle.
Radius : In a circle or sphere the radius is the distance between the center and the boundary.
Square centimeter : Square centimeter or $cm^2$ is a unit of measurement for measuring area. 1 square centimeter is the area of a square with side length 1 $cm,$ so 10,000 $cm^2$ are one $m^2.$
What is the area in square cm of a circle with radius $r=9 cm$? Approximate $\pi$ by 3 in the calculation.