Movement of the Decimal Point

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🎬 Math Angel Video: Decimal Shifting Rules Explained

Multiplying and Dividing Decimals by 10, 100, 1000

Shifting the decimal point in division and multiplication, showing how the decimal point shifts left for division and right for multiplication.

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🛎️ How to Multiply Decimals by Powers of 10?


When multiplying a number by 10, 100, or 1000, move the decimal point 1, 2, or 3 places to the right, respectively.  For example:

  • $12.34 \times 10 = 123.4$   (move 1 place)
  • $12.34 \times 100 = 1234$   (move 2 places)
  • $12.34 \times 1000 = 12340$   (move 3 places)


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Moving the decimal point to the right makes the number larger.

 

🛎️ How to Divide Decimals by Powers of 10?

When dividing a number by 10, 100, or 1000, move the decimal point 1, 2, or 3 places to the left, respectively. For example:

  • $12.34 \div 10 = 1.234$   (move 1 place)
  • $12.34 \div 100 = 0.1234$   (move 2 places)
  • $12.34 \div 1000 = 0.01234$   (move 3 places)


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Moving the decimal point left makes the number smaller.

How to Move the Decimal Point (Examples)

Examples on how to move the decimal point when calculating 5.02*1000, 4.21/100, and 56.7%*10.

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  • Multiplication by 1000 means moving the decimal point 3 places to the right.

$$5.02 \times 1000 = 5020$$

 

  • Division by 100 means moving the decimal point 2 places to the left.

$$4.21 \div 100 = 0.0421$$

 

  • To convert a percentage to a decimal, divide by 100.
    $$56.7\% = \frac{56.7}{100} = 0.567$$

    Then, multiplying by 10 means moving the decimal point 1 place to the right.
    $$0.567 \times 10 = 5.67$$

Shifting the Decimal Point to Convert Between Units

Converting 2.8 metres to 280 centimetres by multiplying by 100, and converting 0.0028 kilometres to metres by multiplying by 1000.

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  • To convert 2.8 meters to centimeters, multiply by 100 because 1 m = 100 cm.

    • $2.8 \times 100 = 280$
    • Therefore, 2.8 m is equal to 280 cm.

 

  • To convert 2.8 meters to kilometers, divide by 1000 because 1 m = $\frac{1}{1000}$ km.

    • $2.8 \div 1000 = 0.0028$
    • Therefore, 2.8 m is equal to 0.0028 km.

🍪 Quiz: Practice Decimal Place Movement

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