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Parts of a Circle
Predictions and Backwards
Calculate Circumference with Diameter
Calculate Circumference with Radius
Word Problems
100
What is circumference?
The boundary of a circle; the length of this boundary
100
How can you predict the circumference of a circle if you only know the diameter?
Multiply the diameter by 3 to get an approximate circumference.
100
What is the formula for calculating the circumference of a circle if you know the diameter?
C = πd C = 3.14(d)
100
What is the formula for calculating the circumference of a circle if you know the radius?
C = 2πr C = (2)(3.14)(r)
100
At a zoo, the giraffes are fenced inside a circular field with a radius of 700m. What length of fencing is needed.
4398.23m
200
What is the radius?
A line segment from the center of the circle to any point on the circumference; the length of this line segment
200
How can you predict the circumference of a circle if you only know the radius?
Multiply the radius by 6 to get an approximate circumference.
200
d = 72cm
C = 226.19
200
r = 0.40mm
C = 2.51mm
200
The distance around a circular wading pool is 39.25m. How far does the lifeguard have to walk from the edge of the pool to get to the center of the pool?
6.25m
300
What is the diameter of a circle?
A line segment that connects two points on the circumference of a circle by going straight through the center of the circle; the length of this line segment
300
You want to buy an area rug, but you don’t have a calculator. You know that the diameter of the rug is 1.5m. Approximately how far around is the rug?
The circumference of the rug is approximately 4.5m
300
d = 33.7cm
C = 105.87cm
300
r = 9cm
C = 56.55cm
300
A patio umbrella has a diameter of 2.5m. Calculate the length of fringe needed for the edge of the umbrella.
7.85m
400
What is a chord and an arc?
A chord is any line segment that connects two points on the circumference of the circle (the diameter is the longest chord possible). When a chord is drawn, it automatically creates two arcs. Arcs are the curved segments of the circumference between each point at the end of the chord.
400
How do you calculate the diameter of a circle if you know the circumference?
Divide by 3.14 to get the diameter.
400
d = 11m
C = 34.56m
400
r = 22.25m
C = 139.80m
400
George Ferris constructed the original Ferris wheel at the midway in Chicago in 1893. The diameter of the ride was 76 m. a) Calculate the circumference. b) If one ride consists of three complete turns of the wheel, how far would you travel in one ride?
a) 238.76m b) 716.28
500
What is pi?
The ratio of the circumference to the diameter of a circle. The value of pi is 3.141592... or about 3.14
500
Calculate the diameter of a circle with the circumference 101.1cm
d = 32.2cm
500
d = 3.14m
C = 9.86m
500
100cm
C = 628.32cm
500
This racetrack consists of a rectangle and two semicircles. What is the length of one lap? Rectangle: l = 60.5m w = 40.5m Semicircle: r = 20.25m
C = 248.23m