Circles Review

Parts of a Circle

100

What is the proper word for "width of a circle."

Diameter

200

What is the proper word for "perimeter of a circle."

Circumference

300

What is the proper word for "distance from the centre to the edge of a circle."

Radius

400

What is the formula for area?

A = pi x r²

500

What is the formula for circumference?

C = pi x d

Circumference

100

Determine the circumference:

d = 18 cm

C = pi x d
   = 3.14 x 18
   = 56.52 cm

200

Determine the circumference.

r = 12 m

C = pi x d
   = 3.14 x 24
   = 75.36 m

300

Determine the circumference.

d = 15 km

C = pi x d
   = 3.14 x 15
   = 47.1 km

400

Determine the circumference.

r = 3.5 m

C = pi x d
   = 3.14 x 7
   = 21.98 m

500

Determine the circumference.

d = 190 mm

C = pi x d
   = 3.14 x 190
   = 596.6 mm

Area

100

Determine the area.

r = 12 m

A = pi x r²
   = 3.14 x 12²
   = 3.14 x 144
   = 452.16 m²

200

Determine the area.

d = 16 km

A = pi x r²
   = 3.14 x 8²
   = 3.14 x 64
   = 200.96 km²

300

Determine the area.

r = 11 cm

A = pi x r²
   = 3.14 x 11²
   = 3.14 x 121
   = 379.94 cm²

400

Determine the area.

d = 6 mm

A = pi x r²
   = 3.14 x 3²
   = 3.14 x 9
   = 28.26 mm²

500

Determine the area.

d = 10 cm

A = pi x r²
   = 3.14 x 5²
   = 3.14 x 25
   = 78.5 cm²

Reverse Problems

100

The circumference of a circle is 59.66 cm.

What is the diameter?

d = 19 cm

200

The circumference of a circle is 81.64 m.

What is the diameter?

d = 26 m

300

The circumference of a circle is 370.52 km.

What is the diameter?

d = 118 km

400

The area of a circle is 78.5 m²

What is the radius?

r = 5

500

The area of a circle is 200.96 cm²

What is the diameter?

d = 16 cm

(because r = 8 cm)

Word/Application

100

A clock has a width of 10 inches. What is the area of the clock?

A = pi x r²
   = 3.14 x 5²
   = 3.14 x 25
   = 78.5 in²

The clock's area is 78.5 in².

200

A circular frying pan is 14 inches wide. How much space is there in the frying pan, to cook food?

A = pi x r²
   = 3.14 x 7²
   = 3.14 x 49
   = 153.86 in²

The frying pan has 153.86 in² of space for cooking.

300

A circular window is 22 cm wide. How much room is there to look through the window?

A = pi x r²
   = 3.14 x 11²
   = 3.14 x 121
   = 379.94 cm²

The window has 379.94 cm² to look through.

400

A roller coaster has a loop with a width of 200 ft. What is the length of the entire loop?

C = pi x d
   = 3.14 x 200
   = 628 ft

500

The wheel of a bicycle has a width of 46 cm. What is the distance the bike will travel, if the wheel fully turns 200 times?

C = pi x d
   = 3.14 x 46
   = 144.44 cm

144.44 x 200 turns = 28,888 cm

The bike will travel 28,888 cm.
(*Bonus: The bike will travel 288.8 m)