Pre-Algebra Examples

$- 2 \cdot 15$

Step 1

Multiply using long multiplication.

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Step 1.1

Factor out a $- 1$ .

$- (2 \cdot 15)$

Step 1.2

Multiply $5$ by $2$ . Place the ones digit $(0)$ in the result line and carry the tens digit $(1)$ . There is one result line for each digit in $15$ .


		$2$
$⨯$	$1$	$5$
	$1$	$0$

Step 1.3

Multiply $1$ by $2$ . Place the result in the next column in the result line. There is one result line for each digit in $15$ .


		$2$
$⨯$	$1$	$5$
	$1$	$0$
	$2$

Step 1.4

Add the numbers in each column. In this case, add $0 + 0$ , then place the $0$ in the result line.


		$2$
$⨯$	$1$	$5$
	$1$	$0$
	$2$
		$0$

Step 1.5

Add the numbers in each column. In this case, add $1 + 2$ , then place the $3$ in the result line.


		$2$
$⨯$	$1$	$5$
	$1$	$0$
	$2$
	$3$	$0$


		$2$
$⨯$	$1$	$5$
	$1$	$0$
	$2$
	$3$	$0$

Step 2

The result of $2 \cdot 15$ is $30$ .

$30$

Step 3

Multiply $30$ by $- 1$ .

$- 30$