Question

What is the area of a circle whose radius is 16 cm?

Answer 1

around 804.5714286`cm^2` which is exactly 256`pi`

Explanation:

easily using the formula :
A = `pi*r^2`

take `pi ~~ 22/7`

A = `pi*r^2`
=`22/7 * 16^2cm^2`
=`22/7*256cm^2`
=804.5714286`cm^2`

Extra ~~~
why does the formula works ?
take a circle, cut them into pieces just like cutting a cake,
the more you cut the more fan shape you'll get and the fan shape is likely to be a triangle, take all the triangles and put them together to form a big triangle, the height of the triangle is the radius of the circle, the base of the triangle is the perimeter of the circle which is 2`pi`r,
area of the triangle is `~~` the area of the circle
height x base / 2 = `r*2pi r /2` = `pi r^2` = A