For the data set 7, 5, 10, 11, 12, the mean, x, is 9. What is the standard
deviation?

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Explanation:

The weird or fancy looking E symbol is the greek uppercase letter sigma. It is effectively the english version of S to represent summation. So we add up all the terms to get this. Luckily this has already been done for us in the table where they wrote "sum = 34", so

From here, we substitute this into the formula, along with n = 5 since there are 5 items in the original list

So,

This computes the sample standard deviation. To get the population standard deviation, you'd basically change the "n-1" to simply "n", and the rest of the formula is identical.

idk sry

step-by-step explanation:

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6