Basic Math Examples

21 \cdot 15

$21 \cdot 15$

Step 1

Multiply using long multiplication.

Tap for more steps...

Step 1.1

Multiply

5

$5$ by

1

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

15

$15$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
		$5$ $5$

Step 1.2

Multiply

5

$5$ by

2

$2$ . Place the ones digit

(0)

$(0)$ in the result line and carry the tens digit

(1)

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

15

$15$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$

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

15

$15$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
	$1$ $1$

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

15

$15$ .


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
$2$ $2$	$1$ $1$

Step 1.5

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

5 + 0

$5 + 0$ , then place the

5

$5$ in the result line.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
$2$ $2$	$1$ $1$
		$5$ $5$

Step 1.6

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

0 + 1

$0 + 1$ , then place the

1

$1$ in the result line.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
$2$ $2$	$1$ $1$
	$1$ $1$	$5$ $5$

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.


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
$2$ $2$	$1$ $1$
$3$ $3$	$1$ $1$	$5$ $5$


	$2$ $2$	$1$ $1$
$\times$ $⨯$	$1$ $1$	$5$ $5$
$1$ $1$	$0$ $0$	$5$ $5$
$2$ $2$	$1$ $1$
$3$ $3$	$1$ $1$	$5$ $5$

Step 2

The result of

21 \cdot 15

$21 \cdot 15$ is

315

$315$ .

315

$315$