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Logic and Proofs Videos 13 videos
If you already know what a conditional statement is, then you're smarter than you look. And boy do you look smart.
Indirect proofs (or proofs by contradiction) prove their conclusion by showing that the opposite cannot be true. You can use this in math and in ar...
CAHSEE Math 5.3 Mathematical Reasoning 231 Views
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Description:
Mathematical Reasoning Drill 5 Problem 3. Which of the following could be the integer mentioned?
Transcript
- 00:03
Here’s an unshmoopy question for a rainy day…
- 00:06
An integer between 70 and 110 exists such that it is a multiple of 2, 3, and 5.
- 00:13
Which of the following could be this number?
- 00:15
And here are the options…
- 00:19
Right from the get go, we can eliminate option A, because last time we checked…
Full Transcript
- 00:23
…60 was not between 70 and 110. Option B can also be eliminated because 75
- 00:29
is odd, which means it can’t be a multiple of 2.
- 00:31
Yay, elementary school math!
- 00:34
The next easiest step would be to eliminate C...
- 00:36
…because the ones digit of 84 isn’t 5 or 0, which means it’s not a multiple of 5.
- 00:42
And there you go!
- 00:43
We only have one option left. Sure enough, 90 is a multiple of 2, 3 and 5.
- 00:48
So our answer is D.
- 00:49
As in, “Divides evenly.”
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