Vocabulary
A line from the center of a circle to the circle
Radius
Formulas for diameter
2πr or πd
r = 999cm
A = ? (round to the hundredths place)
A = 3133723.1cm squared
d = 10
r = ? (round to the nearest hundredth)
r = 5
π is used as ?
3.14
The outline of a circle
Circumference
Formula for area
πr2
The diameter of a circle is 3.14m long. What is the circumference of the circle? (round to the nearest hundredth)
d = 12349m
r = ? (round to the nearest hundredth)
r = 6174.5m
What is the formula for circumference from area?
C = 2(square root(πA)
A line from one point of the circle, through the center and then to another point of the circle
Diameter
Formula for radius from area
(A/π) square rooted
Nate wants a new basketball rim. Nate wants the basketball rim to have an area of 142cm. What is the diameter of the basketball rim? (round to the nearest hundredth)
d = 13.45cm
C = 999πcm
r = ? (round to the nearest hundredth)
r = 499.5cm
If there is a question with the area of any number x π, what is an easy way to find area without any extra step?
Ex: A = 566πm r = ? (round to the nearest hundredth)
You can remove pi from the equation to find radius: (566π/π)square root) = 566 square root, and then just square root that number: (566 square root).
Ex: r = 23.79m
the whole inside space of the circle
Area = 21.26m2
r = ? (round to nearest hundredths place)
r = 2.6m
Greg plays hockey and decides to make a new puck. The new puck has a area of 457mm squared. What is the diameter of Greg's puck? (round to the nearest hundredths)
C = 75.76mm
Hasan finds the circumference of a pizza which is 21cm. What is the radius of the pizza? (round to the nearest hundredth)
r = 3.34cm
What formulas uses square root?
A line segment joining any two points on the circumference of the circle
Chord
r = 150mm
C = ? (round to the hundredths place)
C = 942mm
A circle has an area of 9000m. What is the circumference of the circle? (round to the nearest hundredth)
C = 336.21m
Ms. D corrects a student's worksheet. The worksheet has a problem with a circle which has an area of 1400πmm. What is the radius of the circle? (round to the nearest hundredth)
r = 37.42mm
What is π?
π is the ratio of a circle's circumference to a circle's diameter.