Multiply Large Numbers Quickly With the Box Method

The Box method, which is also called the lattice method, will help you to multiply large numbers quickly. Find out how to use the Box method after the jump.

Steps

  1. Get a piece of paper. Graph paper is best but if not make a grid on the paper.
  2. Draw lines diagonally through certain boxes going down and to the left as in the illustration.
  3. Write one of the factors on the top of the grid, one digit in each box, then the other on the right in the same way.
  4. In each of the halved boxes multiply the two digits that correspond with the box, the ones that would be its coordinates in a grid map. Put the tens digit on the top left side of the line and the ones digit on the bottom right side. If you end up with a one digit answer write a zero as a placeholder where you would have put the tens digit.
  5. Add up the digits in each diagonal column formed by the diagonal lines. Start on the right and work left.

Tips

  • You can do this with any size number, but the larger the number the larger the piece of paper you will need.
  • You should make the grid large enough so that you don't have trouble figuring out what is where later.
  • This works for any number because the diagonals are the place values. (ones, tens, 100's, etc.)

Warnings

  • Don't forget the numbers you have to carry over during the addition.

Things You'll Need

  • Paper (Graph is best but anything works.)
  • Writing implement
  • Multiplication problem
  • Basic knowledge of multiplication and addition

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