Pre-Algebra Examples

$- 12.8 \cdot - 0.0001$

Step 1

The result of multiplying two negative numbers is a positive number.

$12.8 \cdot 0.0001$

Step 2

Multiply $1$ by $8$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
					$8$

Step 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 $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
				$2$	$8$

Step 4

Multiply $1$ by $1$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$

Step 5

Multiply $0$ by $8$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
				$0$

Step 6

Multiply $0$ by $2$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
			$0$	$0$

Step 7

Multiply $0$ by $1$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$

Step 8

Multiply $0$ by $8$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
			$0$

Step 9

Multiply $0$ by $2$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
		$0$	$0$

Step 10

Multiply $0$ by $1$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$

Step 11

Multiply $0$ by $8$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$
		$0$

Step 12

Multiply $0$ by $2$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$
	$0$	$0$

Step 13

Multiply $0$ by $1$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$

Step 14

Multiply $0$ by $8$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
	$0$

Step 15

Multiply $0$ by $2$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


			$1$	$2$	. $8$
$⨯$	$0$	. $0$	$0$	$0$	$1$
			$1$	$2$	$8$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
$0$	$0$

Step 16

Multiply $0$ by $1$ . Place the result in the next column in the result line. There is one result line for each digit in $0.0001$ .


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$

Step 17

Add the numbers in each column. In this case, add $8 + 0 + 0 + 0 + 0$ , then place the $8$ in the result line.


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
						$8$

Step 18

Add the numbers in each column. In this case, add $2 + 0 + 0 + 0 + 0$ , then place the $2$ in the result line.


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
					$2$	$8$

Step 19

Add the numbers in each column. In this case, add $1 + 0 + 0 + 0 + 0$ , then place the $1$ in the result line.


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
				$1$	$2$	$8$

Step 20

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


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
			$0$	$1$	$2$	$8$

Step 21

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


				$1$	$2$	. $8$
	$⨯$	$0$	. $0$	$0$	$0$	$1$
				$1$	$2$	$8$
			$0$	$0$	$0$
		$0$	$0$	$0$
	$0$	$0$	$0$
$0$	$0$	$0$
		$0$	$0$	$1$	$2$	$8$

Step 22

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 $5$ , so the answer must have $5$ decimal places as well.

$0.00128$