exercise: circle area and perimeter problem 1
A circle has a radius of 9 cm.
a) Calculate the diameter
b) Calculate the the perimeter/circumference of the circle.
c) Calculate the area of the circle
answer: circle area and perimeter problem 1
a) answer diameter
d = 2 * r
d = 2 * 9
d = 18 cm
A: The diameter of the circle is 18 centimeter.
b) answer perimeter
P = d * π
P = 18 * π (π = 3.1415..)
P = 56.55 cm
A: The perimeter of the circle is 56.55 cm.
c) answer area
A = r² * π
A = 9² * π
A = 254.47 cm²
A: The area of the circle is 254.47 square centimeters.