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ACT Math 4.1 Pre-Algebra 385 Views
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Description:
ACT Math: Pre-Algebra Drill 4, Problem 1. What could the number described in the video be?
Transcript
- 00:03
Here's your shmoop du jour: Take the absolute value of the full quantity
- 00:07
of seven less than two times a number. That quantity equals 1.
- 00:11
What could the number be?
- 00:17
And here are the potential answers...
- 00:22
Whoa... tricky. What are we doing here, trying to solve a riddle so a troll will let us over his bridge?
Full Transcript
- 00:28
Alright, it's a bit wordy, but let's just write this out in math-ese...
- 00:36
It says... take the absolute value -- that's these straight line thingies...
- 00:40
It says "of"... anything "of" is gonna go inside the straight line thingies -- so
- 00:46
that quantity is...
- 00:47
2x minus seven.
- 00:48
See how we did that? Just kinda reversed the order there.
- 00:53
Then this whole absolute value thing equals 1.
- 00:56
So what are the numbers that could fulfill this solution for x?
- 01:00
Well, maybe we just start with the answer set they give us. Could it be A, which is
- 01:05
negative 4? Well, let's try it.
- 01:07
We have 2 times negative 4, which is negative 8... then we subtract 7 to get negative 15...
- 01:13
which, uh... does not equal 1. At least not in the U.S. Choice A can go bye-bye.
- 01:19
Alright, let's try B... 3.
- 01:21
2 times 3 is 6; subtract 7 to get negative 1... but we are taking the absolute value
- 01:26
here so it's... just 1.
- 01:28
Yeah, 3 works. So the answer is either B or E; we'll have to try C, or 4, to be sure.
- 01:34
If we plug in 4 for x we get 2 times 4, which is 8... then subtract 7, and we have 1.
- 01:40
The absolute value thingy doesn't matter for positive numbers so yeah -- x equals 1 here.
- 01:45
C is true as well, so the answers are both B and C or in this problem...
- 01:50
...the answer is E.
- 01:51
As in, "Evil troll."
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