Radius & Diameter
Circumference and Area
Formulas
Circles in the real world.
100

The diameter is 10 inches. Find the radius.

What is 5 inches.

100

A circle has a diameter of 12.5 inches. What is the circumference in terms of pi?

What is 12.5pi inches? or 39.25

100

If you know the diameter, how do you find the radius?

What is "divide by 2"?

100

A bicycle wheel has a radius of 1 foot. What is the diameter?

2 ft

200

The diameter is 25 feet. Find the radius.

What is 12.5 feet.

200

A circle has a diameter of 25 inches. What is the circumference rounded correctly to 2 decimals (no pi in the answer)?

What is 78.54 inches

200

2*pi*r

What is the circumference?
200

A large Jeep has a tire with a radius of 18 inches. Find the circumference of the wheel.

What is 36pi?

or 113.04

300

The diameter of a circle is 18 inches. Find the radius.

What is 9 inches.

300

A circle has a radius of 50 miles. What is the area of the circle TO THE NEAREST MILE?

What is 7854 miles squared.

300

Area of a circle

What is pi*r^2?

300

Matt is learning to drive a car. The steering wheel in his car has a radius of 9 inches. What is the circumference of the wheel?

What is 56.52 in?


400

The radius of this circle is 10 inches squared. Find its diameter.

What is 20.

400

A circle has a diameter of 16. Find the area in terms of pi.

What is 4(y^2)pi

400

Finding radius when given circumference

C/2pi = r

400

John owns a circular pool in his back yard. If he swims around the outer edge of the pool, he swims 30pi meters. What does this measure??

What is the circumference. 

500

A circle has a diameter of 1000 cm. Find its radius. 

What is 500 cm.

500

A circle has a radius of 10 cm. What is it area? 

What is 314 sq cm?

500

pi * r squared

What is the area of a circle?

500

A circle has a diameter of 28 inches. What is the area of the circle?

What is 615.44 sq in?

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