Area and Circumference of a Circle

Circumference and Area of Circle

Warm Up:

• What formula can be used to find the circumference of a circle?

• What formula can be used to find the area of a circle?

Area

or

Circumference?

​Learning Targets:

• I can decide whether a situation about a circle has to do with area or circumference.

• I can use formulas for circumference area of a circle to solve problems.

Circumference of a Circle

• The Distance AROUND the outside of a circle

• "Edge"

• "Outside"

• "Around"

• "Fence"

Area of a Circle

• Inside of a shape.

• "Cover"

• "Inside"

Multiple Choice

If the word problem is asking you to find the space inside the circle, which formula should you use?

• r = d/2
• d = 2r
• C = πd
• A = πr²

Multiple Choice

If the problem asks you to find the distance around a circle, which formula should you use?

• r = d/2

• d = 2r

• C = πd

• A = πr²

Multiple Choice

A circular swimming pool is 21 feet in diameter.

If you want to build a walkway around the pool, should you find area or circumference?

• area

• circumference

Multiple Choice

A circular swimming pool is 21 feet in diameter.

If you want to build a walkway around the pool, how long will the walkway need to be?

• 65.9 feet

• 1384.7 feet

• 34.5 feet

C = 65.9 feet C = 65.9 feet

Multiple Choice

A circular swimming pool has a radius of 7 feet.

How many square feet of tarp would be needed to cover the pool? In order to answer this question, do you need to find area or circumference?

• area

• circumference

Multiple Choice

A circular swimming pool has a radius of 7 feet.

How many square feet of tarp would be needed to cover the pool?

• 22.0 squared feet

• 44.0 squared feet

• 153.9 squared feet

A = 153.9 squared feet

Multiple Choice

The Jones family wants to enclose their circular garden with a fence. To the nearest foot, what is the minimum length of fencing they need to buy? In order to answer this question, do you need to find area or circumference?

• area

• circumference

Multiple Choice

The Jones family wants to enclose their circular garden with a fence. To the nearest foot, what is the minimum length of fencing they need to buy?

• 196.3 ft

• 392.5 ft

• 785.2 ft

Multiple Choice

Alex has trained his puppy, Popper, to jump through a ring. According to Alex's measurements and calculations, the ring has a radius of 3.5 feet. In order to figure out how much space the puppy has to jump through, would you find the area or the circumference?

• area

• circumference

Multiple Choice

Alex has trained his puppy, Popper, to jump through a ring. According to Alex's measurements and calculations, the ring has a radius of 3.5 feet. How much space does the puppy have to jump through?

• 150.9 squared feet

• 76.9 squared feet

• 38.5 squared feet

A = 38.5 squared units

Multiple Choice

The spray from a spinning lawn sprinkler makes a circle with a 20 foot radius. If Ben and his friends want to play and get wet, how much space do they have? In order to answer this question, do you need to find area or circumference?

• area

• circumference

Multiple Choice

The spray from a spinning lawn sprinkler makes a circle with a 20 foot radius. If Ben and his friends want to play and get wet, how much space do they have?

• 1256 square feet

• 63 square feet

• 1045 square feet

A = 1256 squared feet

Poll

How do you feel about understanding?

Identifying area or circumference in real world contexts

• Exceeding Target: I can show my complete knowledge of this target and beyond.

• Achieving Target: I can show my complete knowledge of this target.

• Progressing Towards Target: I can show my partial knowledge of this target.

• Not Met: I can't show my progress towards this target yet.