Radius
What is a radius?
The distance from the center of a circle to the circumference.
What is the diameter?
The distance from side to side through the center of a circle.
What is the formula for circumference?
C = d x pi
or
C = 2 x pi x r
What is the formula for the area of a circle?
A = pi x r2
What is the radius of a circle with a diameter 800m?
r = 400m
Find the diameter of a circle with radius 7cm.
d = 14cm
Find the circumference of a circle with a diameter of 3ft. (Round to 2 decimal places)
C = 9.42ft
Find the area of a circle with a radius of 9mi. (Round to the nearest 10th)
A = 254.5mi2
What is the relationship between radius and diameter?
r=(d/2)
or
The radius is half the length of the diameter.
What is an equation for the diameter?
d=2 x r
Find the circumference of a circle with a radius of 62in. (Round to 3 decimal places)
C = 389.557in
What is the area of a circle with a diameter of 83km? (Round to the nearest whole number)
A = 5,411km2
The circumference of a soda can is 6.69in. What is the radius of a soda can? (Round to the nearest 100th)
r = 1.06in
The circumference of a steering wheel is 47.12in. What is the diameter of the steering wheel? (Round to the nearest whole number)
d = 15in
The diameter of a Ferris wheel is 50ft. If you go around 5 times, how "far" did you travel? (Round to the first decimal place)
C = 785.4ft
The circumference of a soup can is 11in. What is the area of the lid of the can? (Round to 2 decimal places)
A = 9.63in2
The area of an Olympic medal is 2827.4mm2. What is the radius of an Olympic medal? (Round to the nearest whole number)
r = 30mm
The area of a DVD is 113.097cm2. What is the diameter of the DVD? (Round to the nearest whole number)
d = 12cm
The area of a is 76.5in2. What is the circumference of the plate? (Round to the nearest whole number)
C = 31in
A half gallon of paint will cover 70ft2. Your mom asked you to paint her a giant target on her wall. The wall is 10ft high. Would you have enough paint to paint a target that goes from floor to ceiling?
The area of a 10ft tall circle is 78.54ft2, so no, there would not be enough paint for mom's target.