Math 7 9.1.1 thru 9.1.3

Math 7

9.1.1 thru 9.1.3

Thought of the day!

Learning Objective

I can discover the circumference and surface area of a circle.

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The circumference of a circle can be calculated using $2\pi r$ . For this question round your answer to the nearest 0.1 (tenth). Use 3.14 for $\pi$ .

What is the circumference of a bicycle wheel with a 27-inch diameter?

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Circumference = $2\pi r$

Use 3.14 for $\pi$

If the distance from the center of a Ferris wheel to one of the seats is approximately 90 feet, what is the distance traveled by a seated person, to the nearest foot, in one revolution.

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The Earth has a diameter of 7926.41 miles. What is the circumference of the earth? (Round your answer to the nearest 0.1 tenth)

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Skeeter, the wonder dog, jumps through circular rings as part of his dog show exhibition. Skeeter requires a width of 18 inches for his costume to clear the ring. Will a ring with an inner circumference of 18-inches be large enough for skeeter's act?

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Mr. Barney's circular garden is 4 feet from the center to the outside edge. He wants to build a small fence to keep the neighborhood dogs from getting in his garden. Fencing material is sold by the foot. How many feet of fencing will Mr. Barney need to buy? (Round answer to nearest foot)

Alright, now that we have our rectangle with the area base times height let’s see if this will help us to find the area of a circle. Take your paper and draw a circle. Any circle will do as long as it is a perfectly round circle.

What shape do you see?

1. Cut the circle in half.

2. Now cut the half circles in half so that your circle is now in fourths.

3. Now, when we divide the fourths in half we will end up with eighths.

4. Once you have a circle that has 8 pieces arrange it as follows.

1. What shape do you see now?

2. Make a guess at what the area of the circle will be knowing that we have half of the circle on top and on bottom.

Next cut all of your circle pieces in half so you end up with 16 pieces that you can re-arrange as follows:

​https://youtu.be/YokKp3pwVFc

​Use the following link to watch a short video about how the area of a circle is like the area of a rectangle.

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Find the area of the circle.

A= $\pi r^2$

(Round your answer to the nearest 0.1 tenth)

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Find the area of the circle.

A= $\pi r^2$

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Find the area of the circle.

A= $\pi r^2$

(Round you answer to the nearest 0.01 hundredth)

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Find the number of paint cans needed to paint the helicopter pad.

Round your answer to the nearest full paint can. Use 3.14 for $\pi$ .

Jim is painting the inside of a circular helicopter pad. How many cans of paint would he need if the pad is 50 feet across and each can of paint covers about 200 $ft^2$ .