7.9B Determine the Circumference and Area of circles.

7.9B Determine the Circumference and Area of circles.

Multiple Choice

What is the radius of this circle?

• 18

• 10

• 9

• 8

Multiple Choice

What is the radius?

• 18
• 72
• 38
• 14

Multiple Choice

What is the diameter?

• 5 in
• 10 in
• 3.14 in
• 15.84 in

Multiple Choice

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

• Radius

• Diameter

Multiple Choice

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

• Radius
• Diameter

Multiple Choice

What does "area" mean?

• Space a circle takes up

• Distance around a circle

• Line from one side of a circle to another

• Line from center of circle to side

Multiple Choice

What does "circumference" mean?

• Space a circle takes up
• Distance around a circle
• Line from one side of a circle to another
• Line from center of circle to side

Formulas to use

• Circumference is 2 times π times radius

• Area is π times radius to the power of 2

• Remember that π is used as 3.14

Multiple Choice

When following the formula, what would you do if they give you the diameter?

• Multiply by 2

• Divide by 2

• Add by 2

• Subtract by 2

Multiple Choice

How are the diameter and radius related?

• They're cousins

• Diameter is half of the Radius

• Radius is half of the Diameter

• They're brothers

Diameter and Radius

• Diameter is twice the Radius

• Radius is half of the Diameter

This is the formula to use if they give you the radius or diameter in order to find Circumference.

Here's an example to find the Area.

Multiple Choice

What is π?

• A food

• 3

• 3.1

• 3.14

Multiple Choice

What does $r^2$ mean?

• Radius  $\times$   radius

• Radias  $\times$   2

• Alien language

•  $r\$ with a 2 on top

Multiple Choice

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

Multiple Choice

The diameter of a circle is 3 centimeters. What is the circumference?

• 11.5cm2
• 9.42 cm2
• unicorns are awsome
• 45.3 cm2

Multiple Choice

Find the circumference (to the nearest whole number)

• 88 in
• 44 in
• 116 square in
• None of the above

Multiple Choice

A circular swimming pool is 21 feet in diameter.
How many feet around is the pool?

• 10.5 ft
• 42 ft
• 65.94 ft
• 131.95 ft

Multiple Choice

what is the circumference of this circle ?

• 3.14 cm 
• 37.68 cm
• 24 cm
• 68.4 cm

Multiple Choice

What is the area of this circle?

• 82.13
• 78.5
• 314.16
• 170.12

Multiple Choice

What is the area of this circle?

• 6082.12
• 1519.76
• 1893.14
• 1292.92

Multiple Choice

Find the area of the circle

• 56.52
• 254.34
• 1017.36
• 113.04

Multiple Choice

The diagram below shows the radius of the circular opening of a drinking cup. Which of the following is closest to the circumference of the opening in centimeters?

• 12 cm

• 50 cm

• 25 cm

• 8 cm

Multiple Choice

The diagram below shows the radius of the circular opening of a drinking cup. Which of the following is closest to the circumference of the opening in centimeters?

• 12 cm

• 50 cm

• 25 cm

• 8 cm