Multiplying large numbers - lattice method

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Multiplying large numbers - lattice method

• Created by Sabrina Edmondson
• Adapted from BBC online

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Multiplying large numbers - lattice method

• This method is also called
• Napier's bones.
• In some ways it is similar to the grid method as
  it involves multiplying rows and columns, but it
  gives you a better way to add the results at the
  end of the calculation.

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Multiplying large numbers - lattice method

• With this method, you multiply each number in
  the column by each number in the row. Then you
  add along the diagonals to get the answer.
• Have a look at this equation
• 25 x 5

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Multiplying large numbers - lattice method

• Step 1
• Make a grid with diagonal lines as shown below.
  Split the 25 into a 2 and a 5, putting each digit
  at the top of a column. Put the 5 by the top row.

25
5
Multiplying large numbers - lattice method

• Step 2
• Multiply the columns by the rows, splitting the
  digits up on either side of the diagonal as shown
  here.

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Multiplying large numbers - lattice method

• Step 3
• Finally, add along the diagonals to get your
  answer.

So 25 x 5 125
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Multiplying large numbers - lattice method

• This method is a bit complicated. Talking
  yourself through each step as you do it can be
  useful - someone is sure to ask you what you're
  doing and you'll end up explaining to them!

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Multiplying large numbers - lattice method

• Lets look at another multiplication equation
  worked out using the lattice method.
• With this method, you multiply each number in
  the column by each number in the row. Then you
  add along the diagonals to get the answer.
• Have a look at this equation
• 25 x 5

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Multiplying large numbers - lattice method
255

• Step 1
• Make a grid with diagonal lines as shown. Split
  the 255 into 2, 5, and 5, putting each digit at
  the top of a column. Split the 25 into 2 and 5,
  putting each digit by a row.

25
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Multiplying large numbers - lattice method

• Step 2
• Multiply the columns by the rows, splitting the
  digits up on either side of the diagonal as shown
  here.

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Multiplying large numbers - lattice method

• Step 3
• Finally, add along the diagonals to get your
  answer.

So 255 x 25 6375