Multiplication Using Grid

Slide1: 

How do I multiply a triple digit number by a double digit? 145 x 67 = ? 267 x 19 = ? I’m sure that you’ll agree that there are many methods that we can use. Which method do you feel most comfortable with? Try your method to solve one of the problems on this page. When you are finished, explain your method to your partner. 156 x 14 = ? 243 x 15 = ? 142 x 12 = ? 142 x 14 = ? 262 x 15 = ?

Slide2: 

Here’s a new method for you to try! My problem is: 145 x 13 = ? Step one: Break the numbers up into their different parts. 145 = 100 + 40 + 5 13 = 10 + 3 Step two: Fill the numbers onto a grid like this. 100 40 5 10 3 x

Slide3: 

Step 3: Begin to cross multiply each number filling the answer into the grid. (This is just like filling in a multiplication square.) 100 40 5 10 3 x 1000 400 50 300 120 15 Step 4: Add up each row of numbers and put your total at the side of the column. 100 40 5 3 x 1000 400 50 300 120 15 1450 435

Slide4: 

Step 5: Simply add the two numbers together to get your final answer. 1 4 5 0 + 4 3 5 1 8 8 5 How easy is that? Therefore: 145 x 13 = 1885 Challenge! Can you use this new method to solve the problem below? 134 x 15 = ?