Dividing Decimals By 10, 100 And 1000

Cut a 3.9 m ribbon into 10 and 100 pieces, and divide any decimal by 10, 100 or 1000 by moving the point left.

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Dividing a Decimal by 10

3.9 ÷ 10: multiply by the reciprocal 1/10.

Write the decimal as a fraction: $3.9 = \frac{39}{10}$ .

Dividing by 10 is multiplying by its reciprocal, $\frac{1}{10}$ :

$\frac{39}{10} \div 10 = \frac{39}{10} \times \frac{1}{10} = \frac{39}{100} = 0.39$

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Example 6: 3.9 m of ribbon cut into 10, then 100 pieces.

Problem. Anuja cuts a 3.9 m ribbon into 10 equal pieces. How long is each? What if she cuts it into 100? (Textbook p. 74, Example 6)

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Divide: move left. Multiply: move right.

Moving the point

÷ 10, 100, 1000 → move the point left 1, 2, 3 places. Add zeroes in front if needed.

× 10, 100, 1000 → move the point right 1, 2, 3 places.

Units: 0.039 m = 3.9 cm = 39 mm.

Fill in the book's ÷10, ÷100, ÷1000, ÷10000 table.

0 of 12 blanks filled

Textbook p. 75. Example row: 18.7 ÷ 10 = 1.87, ÷ 100 = 0.187, ÷ 1000 = 0.0187, ÷ 10000 = 0.00187

21.1 ÷ 10 = , ÷ 100 = , ÷ 1000 = , ÷ 10000 =

0.13 ÷ 10 = , ÷ 100 = , ÷ 1000 = , ÷ 10000 =

A number ÷ 100 = 2.146. The number is , and it ÷ 10 =

A number ÷ 10000 = 0.0058. The number is , and it ÷ 1000 =

Divisions by powers of ten and unit changes.

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0.039 m = ? mm

3.9 ÷ 10: multiply by the reciprocal 1/10.

Write the decimal as a fraction: $3.9 = \frac{39}{10}$ .

Dividing by 10 is multiplying by its reciprocal, $\frac{1}{10}$ :

$\frac{39}{10} \div 10 = \frac{39}{10} \times \frac{1}{10} = \frac{39}{100} = 0.39$

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