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Circumference Videos 9 videos

Perimeter and Circumference
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It's super useful to be able to find the distance around stuff. Like when you’re being pursued by authorities while running around the base of an...

SAT Math 1.1 Geometry and Measurement
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SAT Math 1.1 Geometry and Measurement. What is the circumference of the circle?

SAT Math 10.2 Geometry and Measurement
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SAT Math 10.2 Geometry and Measurement. How far does a point on the outside of the circle travel?

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SAT Math 11.3 Geometry and Measurement 218 Views


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SAT Math 11.3 Geometry and Measurement. How far does a point on the outside of the circle travel?


Transcript

00:02

Here’s your Shmoop du jour, brought to you by the unicycle.

00:06

They're perfect for the person who has great balance and enjoys getting odd looks from strangers.

00:12

A wheel with a radius of 6 inches makes four rotations.

00:16

How far does a point on the outside of the circle travel?

00:20

Use 3.14 for pi and round to the nearest whole number.

00:24

Got it? Let's get to it.

00:26

To figure this thing out, we need to know the circumference of the wheel.

00:30

To calculate the circumference, we multiply pi by the diameter of the circle.

00:35

Since we know the radius of the circle is 6 inches, we can just double that to get the diameter,

00:40

which in this case, is 12 inches. So to get the circumference, we just need

00:44

to multiply 12 inches by pi.

00:47

So let's do it. Twelve inches multiplied by 3.14, gives the wheel a circumference of 37.68 inches.

00:54

But…we’re not done yet.

00:56

The wheel turns four times, so we need to multiply 37.68 by four,

01:02

which will give us the total distance that the wheel travels in four rotations.

01:07

Some quick calculations…and we've got a distance traveled of 150.72 inches.

01:14

Since we’re rounding to the nearest whole number, the answer is 151 inches.

01:19

And one quick note before we ride our unicycle into the sunset…

01:23

To find the circumference of a circle, we can either multiply the diameter of the circle

01:26

by pi, or we can multiply the radius of the circle by pi and then multiply that by two.

01:33

Since the diameter is equal to twice the radius, the answer is the same.

01:38

Alright, now let's hop on that magnificent one-wheeled contraption and…

01:42

…ride like the wind?

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