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CAHSEE Math 5.4 Number Sense 170 Views


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Description:

Number Sense Drill 5 Problem 4. Which of the following is equivalent to the expression?

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Transcript

00:03

And here's your shmoop du jour.

00:05

Which of the following is equivalent to 64 times 1/32 to the 4th times 1/16 to the 5th?

00:13

And here are the potential answers...

00:18

OK, so even if we didn't recognize that each of these numbers is a multiple of 2...

00:23

...we could have glanced at the answer choices and gleaned that fact fast.

00:27

In these kinds of questions we are almost always being asked to convert to powers of

00:31

two... and this question is no exception. So we just convert everything to powers of

00:35

2 and rewrite it.

00:36

It will hurt a bit but the hard work is good for us. Yeah, feel the burn.

00:41

64 is 2 times 2 times 2 times 2 times 2 times 2... or 2 to the 6th.

00:47

32 is 2 to the 5th and 16 is 2 to the 4th.

00:50

The problem now looks like this:

00:55

Note also that when we have exponents in the denominator,

00:58

we can rewrite them as negative numbers...

01:00

...so let's rewrite the problem to account for the fractions.

01:03

Get rid of 'em like they're unwanted body fat...

01:05

and we now have a fully rewritten problem that looks like this:

01:10

First, we multiply the exponents that are being raised to another power like this.

01:16

Once we do that, we can add and subtract the exponents like this...

01:20

...and we get 6 minus 20 minus 20, which is negative 34, and woot, there we go --

01:26

it's answer B. Hope you remembered to stretch first.

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