5. Multiplying and dividing by 10 and 100

• To multiply a number by 10, move the digits one place to the left, adding a zero if necessary.
  58 x 10 = 580
  
• To multiply a number by 100, move the digits two places to the left, adding zeros if necessary.
  58 x 100 = 5800
  
• To divide a number by 10, move the digits one place to the right, adding a zero if necessary.
  4.3 ÷ 10 = 0.43
  
• To divide a number by 100, move the digits two places to the right, adding zeros if necessary.
  4.3 ÷ 100 = 0.043
  
• To multiply or divide by numbers such as 20 or 300, multiply or divide by the 2 or 3 first and then by the 10 or 100.
  To do 24 ÷ 20, you could divide 24 by 2 and then divide that answer by 10.
  24 ÷ 2 = 12
  12 ÷ 10 = 1.2
  
  To do 22 x 300, you could multiply 22 by 3 and then multiply that answer by 100.
  22 x 3 = 66
  66 x 100 = 6600