Basic Math Examples

21 \cdot 18

$21 \cdot 18$

Step 1

Multiply using long multiplication.

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Step 1.1

Multiply

8

$8$ by

1

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

18

$18$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
		$8$ $8$

Step 1.2

Multiply

8

$8$ by

2

$2$ . Place the ones digit

(6)

$(6)$ in the result line and carry the tens digit

(1)

$(1)$ . There is one result line for each digit in

18

$18$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$

Step 1.3

Multiply

1

$1$ by

1

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

18

$18$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
	$1$ $1$

Step 1.4

Multiply

1

$1$ by

2

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

18

$18$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
$2$ $2$	$1$ $1$

Step 1.5

Add the numbers in each column. In this case, add

8 + 0

$8 + 0$ , then place the

8

$8$ in the result line.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
$2$ $2$	$1$ $1$
		$8$ $8$

Step 1.6

Add the numbers in each column. In this case, add

6 + 1

$6 + 1$ , then place the

7

$7$ in the result line.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
$2$ $2$	$1$ $1$
	$7$ $7$	$8$ $8$

Step 1.7

Add the numbers in each column. In this case, add

1 + 2

$1 + 2$ , then place the

3

$3$ in the result line.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
$2$ $2$	$1$ $1$
$3$ $3$	$7$ $7$	$8$ $8$


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$8$ $8$
$1$ $1$	$6$ $6$	$8$ $8$
$2$ $2$	$1$ $1$
$3$ $3$	$7$ $7$	$8$ $8$

Step 2

The result of

21 \cdot 18

$21 \cdot 18$ is

378

$378$ .

378

$378$