Multiplication

 

 

 

Multiplying by 0

Any number multiplied by 0 equals 0.

Multiplying by 1

Any number multiplied by 1 equals that number.

 

Multiplying by 10s

How to multiply by tens:

• Move the decimal point one place to the left in the number ending in zero.
• For example: 8 * 40 would become 8*4
• Do the multiplication (8*4=32)
• Move the decimal point of the product one place to the right (320)

Multiplying two digit by one digit numbers

How to multiply a two digit number by a one digit number
(for example 43 * 2).

• Place one number above the other so that the ones' place digits are lined up. Draw a line under the bottom number.

43
 2

• Multiply the ones' place digits (3 * 2 = 6). Place the six below the line in the ones' place column.

43
 2
 6

• Multiply the digit in the tens' place column (4) by the digit in the ones' place of the second number (2). The result is 4 * 2 = 8. Place the answer below the line and to the left of the 6.

43
 2
86

Multiplying three digit by one digit numbers

How to multiply a three digit number by a one digit number
(e.g. 312 * 3).

• Place one number above the other so that the ones' place digits are lined up. Draw a line under the bottom number.

312
  3

• Multiply the two ones' place digits. (2 * 3 = 6). Place the six below the line in the ones' place column.

  
  312
    3
    6
  

• Multiply the digit in the tens' place column (1) by the digit in the ones' place of the second number (3). The result is 1 * 3 = 3. Place the answer below the line and to the left of the 6.

  
  312
    3
   36

• Multiply the digit in the hundreds' place column (3) by the second number (3). The result is 3 * 3 = 9. Place the 9 below the line in the hundreds' place column.

  
  312
    3
  936

 reference: http://www.aaamath.com/mul.htm#topic1
 http://mathatube.com/multiplication-table-chart.html