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3 years ago

Can someone explain these please?

Mathematics

1 answer:

Dominik [7]3 years ago

8 0

5.
-4=r/20-5

First add 5 to both sides
1=r/20

Then multiply both sides by 20
20=r

Final answer: r=20

7.
(v+9)/3=8

First multiply both sides by 3
v+9= 24

Subtract 9 from both sides
v=15

Final answer: v=15

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3 years ago

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3 years ago

Find each sum.

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The score of a person who did better than 85% of all the test-takers was of 624.44.

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Normal Probability Distribution

Problems of normal distributions can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

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The 85th percentile, which is X when Z has a p-value of 0.85, so X when Z = 1.037.

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$X - 500 = 1.037*120$

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The score of a person who did better than 85% of all the test-takers was of 624.44.

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