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I am looking for a better way to teach 2nd graders, and sometimes 3rd graders how to subtract a single digit number from a two digit number, such as 13-8. They typically want to count down from 13 to 8 to compute the difference. I show them that in subtraction if they add the answer to how much they took away, they will have what they started with. Then I tell them that they can get the answer by figuring out how much they need to add to the subtrahend to get the minuend, using examples rather than these terms. (e.g., for 13-8: "How much do you have to add to 8 to get up to 13?"). It seems the vast majority of the kids just do not get this concept, even though I tutor them individually. The same kids can handle multi-digit subtractions with regrouping galore, but they will still count down for 18-9! Do you have any suggestions?
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