3.4 Multiply Using Partial Products

Day we learned to multiply two digit times two digit numbers using partial products. So we're actually still using the same strategy that we did for less than 3.3. Where we drew the area models by breaking both factors down into expanded form and then multiplying each digit. So we did four 80 times ten is 400. 40 times three is 120. Ten times two is 20 and three times two is 6. And then we added all of those partial products together to get our final answer. However, today, we learned to do that without necessarily drawing that area model. So we would do 20 times 70 is 1400. 20 times 9 is 180. Three times 70 is 210. And three times 9 is 27. Then when you add all of those partial products together, that's your final product. So here's another example down here number 6. We would do 50 times 70 is 3500. 50 times 7 is 350. One times 70 is 70 one times 7 is 7. Then when we add up these partial products, we get our final answer. Our final product. One thing that we have to be really careful of is to line up place values. So make sure you're lining up your thousands place hundreds place tens place and ones place before you add.