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Mean, Median, and Mode Videos 18 videos
The geometric mean of two numbers is the square root of the product. Using proportions, you can set up ratios, cross multiply, and then simplify to...
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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
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;
Full Transcript
- 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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