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ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?
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ACT Math 1.3 Elementary Algebra 301 Views
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Description:
ACT Math Elementary Algebra: Drill 1, Problem 3. Solve for y using substitution.
- Elementary Algebra / Substitution
- Elementary Algebra / Linear equations
- Product Type / ACT Math
- Foreign Language / Arabic Subtitled
- Foreign Language / Spanish Subtitled
- Foreign Language / Korean Subtitled
- Foreign Language / Chinese Subtitled
- Elementary Algebra / Evaluation of algebraic expressions through substitution
Transcript
- 00:03
And here's your shmoop de jour...
- 00:05
Solve for y using substitution: 2x + 4y = 16
- 00:11
x + 3y = 12
- 00:13
And here are the potential answers...
- 00:18
OK, so what is this question asking?
Full Transcript
- 00:21
Questions like this one are algebra's version of... puzzles. Except you don't have to
- 00:25
worry about getting that cardboard dust all over yourself.
- 00:28
The key is to isolate one of the variables cleanly...
- 00:31
...i.e. figure out just what y equals and then shove that result into the other equation
- 00:35
so we can get a real answer.
- 00:38
It doesn't matter which equation we solve, but let's start with the second because...
- 00:42
it's there. And we already have a variable all by its lonesome.
- 00:45
We can rewrite it as x equals 12 minus 3y.
- 00:48
So now, everywhere we see an "x" we can just substitute "12 minus 3y."
- 00:54
If we do so in the first equation, we get 2 times the quantity 12 minus 3y... plus the
- 01:01
4y and equals 16.
- 01:04
Distribute the 2 and we have 24 minus 6y plus 4y equals 16.
- 01:10
Simplify to get 8 minus 2y equals zero...
- 01:13
...and then 8 = 2y.
- 01:16
Then if we divide both sides by 2 and we get y equals... 4.
- 01:21
Answer C.
- 01:22
As in, "Cardboard dust."
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