Finding Diameter and Radius of a Circle

When finding area of a circle, if diameter is given, we need to find radius. We can find radius by ___________ diameter by 2.

• Adding

• Subtracting

• Multiplying

• Dividing

Is the red line a radius or diameter of the circle?

• Radius

• Diameter

If my diameter is 19 inches, what is my radius?

• 38 inches

• 9.5 inches

• 59.66 inches

• 119.32 inches

Jayne has a very large circular lollipop that has a circumference of 25.12 inches. What would the diameter of Jayne’s lollipop be? Use π = 3.14.

• 4 in.

• 8 in.

• 12 in.

• 16 in.

Randy’s circular garden has a radius of 1.5 feet. He wants to enclose the garden edging that costs $0.75 per foot. About how much will the edging cost? 

• $8.00

• $7.00

• $3.50

• $0.50

Alex has trained his puppy, Popper, to jump through a ring. According to Alex's measurements and calculations, the ring has a diameter of 3.5 feet. What is the ring's circumference (use 3.14 for pi)?

• 11.32 ft

• 12.25 ft

• 10.99 ft

• 8.75 ft

Once we have the measurement for radius, we need to __________the radius.

• Square

• Add

• Subtract

• Divide

Square the radius means...

• You add the radius by it self two times.

• You subtract the radius by it self two times.

• You multiply the radius by it self two times.

• You divide the radius by it self two times.

• Diameter

• radius

• Circle

• Wait...I know this!!