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Number Sense Videos 30 videos
Number Sense: Drill Set 2, Problem 5. By what percent did his percentage grade increase from one test to the other?
Number Sense: Drill Set 3, Problem 1. This is a decrease of, approximately, what percent?
Number Sense Drill 3 Problem 3. How much interest will Warren have earned in three years?
CAHSEE Math 2.4 Number Sense 178 Views
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Description:
Number Sense: Drill Set 2, Problem 4. 7 is 3.5% of what number?
Transcript
- 00:03
Here's a boring, unshmoopy question for you that you'll use on an exam somewhere in life...
- 00:08
7 is 3.5% of what number?
- 00:11
Here are your potential answers...
- 00:19
This question is really just as much about understanding English as it is about understanding the math.
- 00:24
In particular, there's one key word you should focus on: Of.
Full Transcript
- 00:28
In math terms, it always means... times.
- 00:32
There is another big-time important 2-letter word here as well: Is.
- 00:36
Which means ... equals.
- 00:37
So in plain English, this question translates to:
- 00:40
7 equals 3.5% times what number? Or 7 equals .035x
- 00:48
One other thing this question is testing is whether we really understand what PERCENT means.
- 00:54
Basically, it means FOR EVERY HUNDRED.
- 00:57
3.5% ain't much... it's only 3 and a half units per hundred.
- 01:01
So when we multiply it all out, we have to stick the zero in the tenths place --
- 01:05
the evil overlords in TestLand will almost certainly try to get us to stumble over this pebble.
- 01:10
But if we got the equation right, then the rest is just about the algebra.
- 01:14
So to solve for x, divide both sides by .035... and we get x equals 7 over .035.
- 01:22
Doing the long division, it looks like this:
- 01:25
And when all's said and done, we have x equals 200... and the answer is D.
- 01:29
Not a super-toughie... you just have to watch out for those pebbles.
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