- Student writes the problem in the grid (e.g. 6 x 417).
- Student then writes the answer to each single digit multiplication in the appropriate square.
- The tens digit is placed above the diagonal; the ones digit below the diagonal.
- When all squares have been completed, the student sums the numbers between each set of diagonals, and writes the sum at the bottom of the grid. NOTE: If the sum is greater than 10, regroup the ten to the next diagonal to the left.
- The student can now simply read the answer from left to right and insert commas, as appropriate.
For a complete overview of this method, see Cool Math's explanation of Lattice Multiplication to view the step-by-step procedure. Take a cue from the site's explanation and use colored markers when introducing this algorithm to students on the overhead or whiteboard.
- Download Lattice Multiplication for a practice page.
- Download Lattice Multiplication Answers for answers to the practice page.