Ask somebody to think of subtraction as the distance between two numbers. Then ask them to find the distance between 464 and 782 by adding up (you may want guide them into using landmark numbers...usually numbers that end in 0 or 00 or 000...). 782 - 464 becomes: 464 + 6= 470 470 + 30 = 500 500 + 282 = 782 In summation, we found the distance to be 6 + 30 + 282. Adding from left to right gives place value sums of 200 (2 is the only hundreds place value digit)+ 110 (the sum of 30 +80) + 8 (6 + 2) or 318. This may look complicated, but all can be done as simple mental math, and the concept works well with all number combinations.
Please remember that you can start thinking this way using really small numbers to help understand. We all know that 10-4 = 6, but if you think about the distance between 4 and 10, it becomes easy to see how we can add-on to 4 until we get to 10 (4 + 6 =10)
Peace,
T-Cubed
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1 comment:
I love it! We are here in Kentucky trying to help teachers reshape their thinking about math. It's funny to see teachers who have been teaching forever say "Ohhhh!" Math is cool. :)
(ps-Love the new blog.)
Ashley Russell
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