Area of a Circle
Radius, Diameter & Circumference of a Circle
Area of a Triangle
Circumference of a circle
100
What is the "radius" of a circle?
The distance from the centre of the circle to a point on the circle
100
Name at least 8 geometric shapes
answers may vary
100
What is the area?
A=(b)(h)
2
A=(6 units)(5 units)
2
A=15 units2 (OR square units)
100
What is the circumference of this circle?
3.14 x 12
37.68
200
Find the area of this circle:
A=ᴨr2
A=(3.14)(4 cm)2
A=(3.14)(4 cm)(4 cm)
A=50.24 cm2
200
What is the "diameter" of a circle?
The distance across a circle through its centre
200
What is the area of this triangle?
A=(b)(h)
2
A=(6 in)(7 in)
2
A=21 in2
200
What is the formula for the circumference of a circle?
pi x diameter
300
Find the area of this circle:
A=ᴨr2
A=(3.14)(12 cm)2
A=(3.14)(12 cm)(12 cm)
A=452.16 cm2
300
What is the circumference of this circle?
C=2ᴨr
C=(2)(3.14)(3 cm)
C=18.84 cm
300
What is the area of this triangle?
A=(b)(h)
2
A=(12 m)(10 m)
2
A=60 m2
300
What is the circumference of this circle?
3.14 x 18
56.52 in
400
The diameter of a circle is 12 in. Find the area of the circle:
r = d
2
r=12 in
2
r=6 in
A=ᴨr2
A=(3.14)(6 in)2
A=(3.14)(6 in)(6 in)
A=113.04 in2
400
What is the circumference of this circle? (" is inches)
C=ᴨd
C=(3.14)(8 in)
C=25.12 in
400
What is the area of this triangle?
A=(b)(h)
2
A=(14 m)(10 m)
2
A=70 m2
400
What is the circumference of this circle
14x2= 28 so 28 is the diameter
3.14 x 28
87.92 cm
500
Ms. K was trying to find the area of this circle but she made a mistake:
What mistake did she make in her work shown below? What is the correct answer?
A=ᴨr2
A=(3.14)(5 cm)2
A=(3.14)(5 cm)(2)
A=31.4 cm2
She multiplied the radius by 2 instead of squaring it.
A=ᴨr2
A=(3.14)(5 cm)2
A=(3.14)(5 cm)(5 cm)
A=78.5 cm2
500
The circumference of a circle is 69.08 ft. What is the radius of the circle?
C=ᴨd
69.08 ft=(3.14)(d)
3.14 3.14
22 ft=d
r = d
2
r = 22ft
2
r = 11 ft
500
What is the base of this triangle?
A=(b)(h)
2
12 cm2=(3 cm)(b)
2
(12 cm2)(2)=(3 cm)(b)(2)
2
24 cm2=(3 cm)(b)
3 cm 3 cm
8 cm = b
500
What is the circumference of this circle?
diameter= 10x2 = 20
circumference = 3.14 x 20
62.8 mm