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SAT Math 4.1 Statistics and Probability 243 Views


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Description:

SAT Math 4.1 Statistics and Probability

Language:
English Language

Transcript

00:03

Here’s your shmoop du jour, brought to you by Math Tests.

00:06

Sometimes, your teachers grade them on a Sine Curve.

00:11

On his last four tests, Ted scored a 71, 86, 77, and 92.

00:17

What must he score on his fifth test to have an arithmetic mean of at least 85?

00:28

He’s looking for the arithmetic mean;

00:30

remember, that's the sum of the data divided by the number of data entries.

00:35

It's another name for the AVERAGE.

00:43

To find out what Ted must score on his fifth test—we'll call it variable T—to have

00:48

an arithmetic mean of at least 85, we can write an equation as follows.

00:52

85 equals the sum of all the tests: 71 plus 86 plus 77 plus 92 plus T divided by 5.

01:03

Let's solve for T now. We start by multiplying both sides by 5.

01:07

We get 85 times 5 is 425. Adding up 71, 86, 77 and 92 equals 326 plus T.

01:15

Subtract 326 from both sides...and we get T equals 99.

01:20

So 99 is our answer. Yikes. Happy cramming, Ted…

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