partial products multiplication 2

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Slide 1  Partial Products Multiplication
 multiply a whole number of up to four digits by a onedigit whole number, multiply two twodigit numbers, using strategies based on place value and the properties of operations and illustrate and explain the calculation by using equations, rectangular arrays and/or area models. (CCSS Math.4.NBT.5)

Slide 2  Why Partial Products?
 uWhen children are first learning multidigit algorithms, they are also still firming up their understanding of place value. It makes sense to have them work with algorithms that help to build their place value understanding, rather than with algorithms that ignore place value.
 uWhen people are doing mental arithmetic, they actually do something much more like the partial products algorithm than like the standard algorithm. Most people find it very difficult to keep track of carried digits when computing in their heads. So the partial products algorithm more closely matches the ways people think about numbers (although it is less efficient for numbers with lots of nonzero digits).
 uThe connection between the partial products algorithm and the ways people work with algebraic expressions is closer than with the standard algorithm.

Slide 3  How does it work?

Slide 4  Watch again with area models:

Slide 5  Now you can try:

Slide 6  What did Lucy do wrong?
 27
 x 35
 20x5= 10
 7x5= 35
 20x30= 600
 7x30= 210
 ________________
 855