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Playlist Logic and Proof 15 videos

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Conditional Statements
2509 Views

If you already know what a conditional statement is, then you're smarter than you look. And boy do you look smart.

1
Formal Proofs
1858 Views

Formal proofs present the oh-so-mathematical evidence in two columns: one for the statement they are claiming is true, and the other for the reason...

2
Indirect Proofs
1734 Views

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...

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CAHSEE Math 2.5 Mathematical Reasoning 201 Views


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Description:

CAHSEE Math Mathematical Reasoning: Drill 2, Problem 5. Which of the following conclusions can be drawn based on the above information?

Language:
English Language

Transcript

00:04

Anyone have a hankering for a slice of piping hot algebra?

00:10

Suppose x = 2m and y = 5n, where m and n are positive integers.

00:17

Which of the following conclusions can be drawn based on the above information on m and n?

00:23

Here are the potential answers...

00:28

Okay, this question wants us to use... reason.

00:30

Not the chocolate kind.

00:32

What can we deduct from the stuff that's given to us?

00:35

Well, let's see. X is equal to 2 times m, which is a positive integer...

00:39

...which means that x must be an even number. Because if we're multiplying ANY positive

00:43

integer by 2, we're going to wind up with something that's even.

00:48

Similar deal with y... except we're multiplying n by 5, so we know y must be a multiple of 5.

00:54

Let's look at our answer choices.

00:56

X is divisible by 3? Um, no... we know it's divisible by 2, and it MIGHT be divisible

01:02

by 3, but we can't be sure.

01:04

X is odd? Definitely not. We just decided it had to be even. Next.

01:08

Y is a negative number? No way. Not if n is positive and being multiplied by 5.

01:14

So it seems like D is going to be the answer to all our prayers, but let's make sure.

01:18

Is x times y a multiple of 10?

01:21

Well, if one is a multiple of 2 and the other is a multiple of 5...

01:25

...then yeah, it makes sense that the two multiplied together would be a multiple of 10.

01:29

Our answer is D. As in, "Disney got it wrong."

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