Circle information
What would you use from your protractor kit to make a circle?
Compass
What does circumference mean?
the distance around a circle
What is the equation for the area of a circle?
A = pi x r x r
what is the area of a circle with a 2.4 cm radius? (to the nearest tenth)
A=3.14x 2.4 x2.4 A=18.1cm^2
What is the distance around the circle divided by diameter?
Pi
What is the equation for circumference? (give both equations one with radius and one with diameter)
c=pi x d or c= pi x 2 x r
If you have a circular mirror with a radius of 20cm, what is its area?
A= pi x 20x 20cm A = 400x 3.14 = 1256 cm2
true or false: If the radius of a circle is doubled, then the circumference is also doubled?
Always true
What is the distance around the circle divided by the radius?
2pi
What is the circumference of a circle if it has a diameter of 5.2 m?
answer: 16.33 m c=3.14 x 5.2 c= 16.33 m
A circle has a diameter of 25cm. What is it's area?
r= 25/ 2= 12.5cm
A=pi x 12.5 x 12.5
= 490.63cm2
True or False: The circumference of a circle is roughly 6x the length of the radius.
True
How do you find the radius when you're given only the diameter?
radius= diameter ÷ 2
If you are given a radius of 6cm, what is the circumference?
12x pi = 37.68
The area of a circle is about how many times the square of its radius? a.1 b.2 c.3 d.4
answer: 3
True or False: If you divided a circle into equal triangles and arranged it into a parallelogram, the height of the parallelogram would be the length of the diameter of the circle. (must draw a diagram to explain)
False, the height of the parallelogram would be the length of the radius of the circle.
What is the radius of a circle with a diameter of 95m? (leave your answer in cm)
4750 cm
What is the diameter of a circle that has a circumference of 221mm?
c= pi x d 221mm = 3.14 x d 221/3.14 =d d=70.38mm
44 m of fencing is used to make a circular fence. What is the area of the circle? (to the nearest square metre)
44 is the circumference
44=3.14 x d
d= 44/3.14 = 14.01/ 2= r
r=7.01
A= pi x r x r
A= 3.14 x 7.01 x 7.01 A=154 m2
A Canadian loonie has a diameter of 28mm. What is the area of the loonie?
A= pi x r^2
r= 28/2 = 14
A= (14x14)x 3.14
= 615.44 mm ^2