Unformatted text preview: More Mental Math Strategies Created by Lori Romano You can rearrange a problem to make it easier. Consider this problem: 256 x 4 We can think of 256 as: (200 + 50 + 6) Now we just multiply each of the addends by 4. Created by Lori Romano 256 x 4
Our new problem looks like this: 4(200 + 50 + 6) The “4” gets distributed over each of the addends. This is called the distributive property of multiplication over addition.
Created by Lori Romano 4(200 + 50 + 6) Distributing the 4 over each of the addends gives us (4 x 200) + (4 x 50) + (4 x 6) 800 + 200 + 24 1,024 Created by Lori Romano Try this one: 453 x 9
First, think of 453 as (400 + 50 + 3) Use the distributive property to distribute the 9 over each of the addends. 9(400 + 50 + 3) Created by Lori Romano 9(400 + 50 + 3) Multiply each of the addends by 9, then find the sum. (9 x 400) + (9 x 50) + (9 x 3) 3600 + 450 + 27 4050 + 27 4,077 Created by Lori Romano 45 x 14
Think of 45 as (40 +5) and 14 as (10 + 4). Set the problem up like this: 10(40 + 5) + 4(40 + 5) Created by Lori Romano 10(40 + 5) + 4(40 + 5)
Now, use the distributive property to multiply (40 + 5) by both 10 and 4. (400 + 50) + (160 +20) 450 + 180 450 + 50 + 130 500 + 130 = 630 Created by Lori Romano Now you try it.
Write 5 multiplication problems and use the rearranging strategy to solve them. Use words to explain how to apply the strategy to solve the problem. Created by Lori Romano ...
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 Spring '08
 ihcsol
 Math, Lori Romano

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