Algebra Examples

$- 7.5$ , $- 9$ , $- 10.5$ , $- 12$

Step 1

The mean of a set of numbers is the sum divided by the number of terms.

$\frac{- 7.5 - 9 - 10.5 - 12}{4}$

Step 2

Simplify the numerator.

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Step 2.1

Subtract $9$ from $- 7.5$ .

$\frac{- 16.5 - 10.5 - 12}{4}$

Step 2.2

Subtract $10.5$ from $- 16.5$ .

$\frac{- 27 - 12}{4}$

Step 2.3

Subtract $12$ from $- 27$ .

$\frac{- 39}{4}$

Step 3

Reduce the expression by cancelling the common factors.

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Step 3.1

Cancel the common factor of $- 39$ and $4$ .

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Step 3.1.1

Rewrite $- 39$ as $1 (- 39)$ .

$\frac{1 (- 39)}{4}$

Step 3.1.2

Cancel the common factors.

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Step 3.1.2.1

Rewrite $4$ as $1 (4)$ .

$\frac{1 \cdot - 39}{1 \cdot 4}$

Step 3.1.2.2

Cancel the common factor.

$\frac{1 \cdot - 39}{1 \cdot 4}$

Step 3.1.2.3

Rewrite the expression.

$\frac{- 39}{4}$

Step 3.2

Move the negative in front of the fraction.

$- \frac{39}{4}$

Step 4

Divide.

$- 9.75$

Step 5

The mean should be rounded to one more decimal place than the original data. If the original data were mixed, round to one decimal place more than the least precise.

$- 9.8$