Precalculus Examples

$22.5 \cdot 2$

Step 1

Multiply using long multiplication.

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Step 1.1

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

		$1$
	$2$	$2$	. $5$
$⨯$			$2$
			$0$

Step 1.2

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

		$1$
	$2$	$2$	. $5$
$⨯$			$2$
		$5$	$0$

Step 1.3

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


	$2$	$2$	. $5$
$⨯$			$2$
	$4$	$5$	$0$

Step 1.4

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


	$2$	$2$	. $5$
$⨯$			$2$
	$4$	$5$	$0$
			$0$

Step 1.5

Add the numbers in each column. In this case, add $5$ , then place the $5$ in the result line.


	$2$	$2$	. $5$
$⨯$			$2$
	$4$	$5$	$0$
		$5$	$0$

Step 1.6

Add the numbers in each column. In this case, add $4$ , then place the $4$ in the result line.


	$2$	$2$	. $5$
$⨯$			$2$
	$4$	$5$	$0$
	$4$	$5$	$0$


	$2$	$2$	. $5$
$⨯$			$2$
	$4$	$5$	$0$
	$4$	$5$	$0$

Step 2

To find the number of decimal places needed in the answer, add the number of decimal places in the multiplier and multiplicand. In this case, there is a total of $1$ , so the answer must have $1$ decimal places as well.

$45$