First Grade Math Subtraction Tables

Video Transcript

"Once your child has completely memorized his or her addition tables, only when they are completely memorized all the way up to the tens, you are then ready to teach memorization of subtraction tables. It's a lot easier once you memorize the addition because subtraction is just the reverse and you can use the same numbers. So in a sense once they've memorized the addition tables they kind of have the subtraction tables already. And you can show them with this neat little diagram called triangle adding and subtracting. Like I'll show you right here. Once they have memorized five plus three equals eight, then they can easily say that means eight minus five equals three and eight minus three equals five and you can emphasize that this top part is a whole and these bottom parts, bottom corners of the triangle stand for different parts of that whole. These two combined will always make the top number and if you break this off of the top number you will get that part and you can make a bunch of these triangles you can have your child come up with them on his or her own and you can even use them to do worksheet problems like this, leave one of the numbers out and then say what problem does this emphasize and it shows that of course sixteen minus (even have them decide if it's a plus or minus) sixteen minus seven equals nine and that's how we do triangle adding and subtracting."