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Plane figures (triangles, rectangles, parallelograms, trapezoids, circles, polygons) Videos 10 videos
ACT Math: Plane Geometry Drill 3, Problem 5. How long would it take for the wheel to make two rotations?
One formula to rule them all, one formula to find them. One formula to bring them all, and in the darkness bind them. Or something like that. I...
ACT Math 3.5 Plane Geometry 394 Views
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Description:
ACT Math: Plane Geometry Drill 3, Problem 5. How long would it take for the wheel to make two rotations?
Transcript
- 00:02
For a good time solve this shmoopy question...
- 00:04
A circular wheel rotates 480 degrees in two minutes.
- 00:09
How long would it take for this wheel to make 2 complete rotations?
- 00:13
And here are the potential answers...
- 00:16
Well it's a plain vanilla ratio question really...
Full Transcript
- 00:19
Something is to something as something else is to something else.
- 00:23
Key things to note: 1 full rotation is 360 degrees...
- 00:28
...so two rotations is 720 degrees...
- 00:31
...480 degrees is 2 minutes or...
- 00:35
...120 seconds as 720 degrees is to what?
- 00:40
So in this case we can just cross multiply here
- 00:43
and we take 480 time x equal 720 times 120.
- 00:48
So the base equation is 480X equals 86400.
- 00:52
Now divide both sides by 480 and get X equals 180 seconds.
- 00:57
That's x equals 180 divided by 60 seconds which is
- 01:03
3 minutes. Looks like C is our answer.