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Equations of Circles Videos 6 videos

ACT Math 5.1 Plane Geometry
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ACT Math: Plane Geometry Drill 5, Problem 1. What is the area of the circle?

SAT Math 10.5 Geometry and Measurement
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SAT Math 10.5 Geometry and Measurement. How many rotations does each tire make?

SAT Math 7.4 Geometry and Measurement
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SAT Math 7.4 Geometry and Measurement

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SAT Math 8.1 Geometry and Measurement 179 Views


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Description:

SAT Math 8.1 Geometry and Measurement

Language:
English Language

Transcript

00:02

Here’s your shmoop du jour, brought to you by bicycles.

00:06

We’re still holding onto the patent for handlebar moustaches…

00:09

A bicycle that has tires with a diameter of 26 inches travels 2 miles.

00:13

Approximately how many rotations did each tire make?

00:17

And here are your potential answers…

00:20

Oh, sure… the “bicycle” traveled 2 miles. No one at all was pedaling the dang thing.

00:25

Sheesh…credit where credit is due, guys…

00:27

All right, what have we got here?

00:29

Each tire of our bike has a diameter of 26 inches… well, that should help us find the circumference.

00:37

The formula we’re looking for is 2 pi r… or pi times d, because 2r is d.

00:42

We already have our d… so...

00:44

The perimeter of each tire is 26 pi inches… or 6.8 feet.

00:53

If we weren’t already a metric conversion whiz, the problem tells us that one mile equals 5,280 feet…

01:00

…so if our bike went TWO miles, then it went 10,560 feet. Which is…a lot of feet.

01:08

All right, well… we’ve got our perimeter… now we want to know how many times each tire

01:12

can turn that 6.8 feet over the course of its 2-mile run.

01:16

We take 10,560 divided by 6.8…

01:19

…and get roughly 1,550 rotations.

01:23

Option E.

01:24

Now I suppose you’re going to give the bike all the credit for solving this problem, too, aren’t you?

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