Lattice Multiplication  The lattice method of multiplication uses a grid with squares and diagonals called a lattice.  How many of you have seen this type of multiplication before?  If you have seen it, how do you know what size lattice to use?  The factors tell which size lattice to use. Write the second factor above the lattice and the first factor on the right side.

Where do you write the partial products on a lattice?  Take a look at page 54 in your workbook.  Where do you write the partial products on the lattice? See the example for help.  -The answers are written in the square where the multiplied digits intersect on the lattice. 1 digit per diagonal.  Multiply the digits. Then Write the answers.  Then add the numbers along each diagonal. Begin with the diagonal in the bottom right-hand corner.  Extend the diagonals outside of the lattice, and place the answers there.

Apply this method  In your ISN, use the lattice multiplication method to find the product of the following problems.  47 * 85  98 * 586  945 * 246  Have a friend check your answers. You may use a calculator to double check.

Lattice Method for decimals  The lattice grid automatically locates the placement of the decimal point in the answer.  When writing the factors above and below the lattice, include the decimal points. In the factor above the grid, the decimal point should be above a column line. In the factor on the right side of the grid, the decimal point should be to the right of a row line.  Locate the decimal point in the answer as follows: Slide the decimal point in the factor above the grid down. Slide the decimal point in the factor on the right side of the grid across. The decimal points will intersect on a diagonal line. Slide that decimal point down along the diagonal line. Place a decimal point at the end of the diagonal line.

Independent Activity  Complete page 55 in your workbook – Multiplication by the Lattice Method. Homework : Study Link 5.9 Page 59 -Multiply with the Lattice Method Enrichment: Page 60 – Exploring an Ancient Multiplication Method (Egyption) Feel free to use a partner!