How are the formulas for the circumference of a circle and area of a circle derived? explain

Step-by-step explanation:

Let O be a circle. Draw diameters of the circle with no of diameters as large as possible such that the circle is divided into equal sectors.

Cut each sector and paste on a paper with one showing point edge down and other sector adjacent to first showing point edge up. Like this we get a trapezium with just one sector left out in our hand. Cut it into half and paste on either end to get a perfect rectangle.

Now we have the rectangle having side as r, and length = a value pi times the radius.

Since the length x2 have to give the circumference because of our activity, we get

circumference = 2pir

Area of circle = area of all sectors =

area of rectangle = length xwidth

=pir (r) = pir^2

$450 is the answer.

step-by-step explanation:

30% of 450 = 135

450-135=315

i got 10.28 but that rounds up to 10.3