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SAT Math 10.5 Geometry and Measurement 192 Views
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Description:
SAT Math 10.5 Geometry and Measurement. How many rotations does each tire make?
Transcript
- 00:03
Here’s your shmoop du jour, brought to you by “riding a motorcycle.”
- 00:07
It’s…just like riding a bike. But with the added near-certainty of serious injury.
- 00:13
A bicycle that has tires with a diameter of 2 feet travels half a mile.
- 00:18
How many rotations does each tire make? There are 5,280 feet in one mile.
- 00:24
Round answer to the nearest whole number.
Full Transcript
- 00:27
So what we’re looking for is the number of rotations…
- 00:31
Well, cleverly, let’s call that… n.
- 00:33
That n for…number of rotations.
- 00:37
All right, we want to know how many times the full circle rotates over the course of its journey,
- 00:42
so the circumference of the tire… times n… equals a half a mile.
- 00:48
If there are 5,280 feet in a mile, then in a half mile that's...
- 00:53
5,280 over 2...that's 2,640.
- 00:58
We know the circumference of a circle is diameter times pi...
- 01:03
…so 2 – the diameter of our tire…times pi times n…equals 2,640.
- 01:11
We want n by itself, so we divide both sides of the equation by 2 pi to get n equals 2,640 over 2 pi.
- 01:21
Now it’s time to put our calculator to work.
- 01:24
2,640 divided by 2 pi comes out to 420.38…
- 01:31
or, when rounded to the nearest whole number… 420 rotations.
- 01:36
Wow… you had so much fun counting tire rotations you barely even remember how you got here.
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