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Subtraction Strategy

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This is another example how students can approach subtraction with reason and simply add up the difference between the two numbers.

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okay today we're going to look at the standard algorithm and how come we somehow take this nonsense and turn it from something completely abstract into something concrete and conceptual that your average student would basically be able to comprehend and concretely come up with some number sensitive answer without going through all these criss cross applesauce step so when you ask students to look at this problem and make some sense of it and ask them what's the first thing they have to do it's a great little assessment and what you're going to see is students are going to point to the ones column in pretty much an why we look over at the ones and so on and so forth and then we get into the next group over here the twos in the ones with we actually know as the tens what we're going to do is change this problem to something concrete that we can understand actually maybe not so much we can understand but your students as we look at this problem we have their what is really the difference between 25 and 17 so we can look at 17 and students can somehow human understand as we look at 17 simply create a vertical number line when we do that we have 17 18 19 20 21 22 23 24 25 three four five six seven eight so the difference between those two numbers is 8 so if I turn this horizontally we can start 17 and we counted up to 25 also great for moving into hundreds and the thousands for difference

Listed in 3rd Grade

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Subtraction Strategy

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