Lattice Multiplication
Lattice multiplication, also known as Indian multiplication, is written in a prepared grid.
If we want to calculate 38 × 27, we write the results of multiplying the individual digits into the boxes divided by diagonals. In our example, 3 × 2 = 6, 8 × 2 = 16, 3 × 7 = 21, and 8 × 7 = 56. If the result of multiplying two digits is less than 10, it is helpful to write 0 in the tens place to keep the grid clear, as shown in the picture below.
When all the digits have been multiplied, we add the numbers along the diagonals from right to left. We write down the ones and carry the tens to the next diagonal. For example, in our picture, 6 + 5 + 1 = 12, so we write 2 in the bottom box and carry 1 to the next diagonal. The digits we get after adding are then read from top to bottom and to the right, and this gives us the final product. In our case, the result is 1026.
