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ACT Math: Pre-Algebra Drill 5, Problem 2. If a and b are prime numbers, how many factors does ab have?
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ACT Math 3.5 Plane Geometry 394 Views
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ACT Math: Plane Geometry Drill 3, Problem 5. How long would it take for the wheel to make two rotations?
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.