To this method’s credit, it doesn’t have the kids draw a bajillion little boxes to represent the numbers. To its discredit, the method complicates a fairly straightforward process for multi-place subtraction by using a method called counting up.
The problem, which is intended for students in Grade 4 (aged 9), asks them to find the difference between 325 and 38. Using the old-fangled method, you stack the numbers with the larger value on top, then “borrow” and subtract:
Borrowing from the tens column, you subtract 8 from 15, which yields 7. Then borrowing from the hundreds column, you subtract 11 from 3, which yields 8. You bring down the 2 in the hundreds column, giving you the answer: 287.
But why bother with all that old hat mumbo jumbo when you can use the new and improved counting up method, which is displayed below.
The traditional way required four operations: two borrowings and two simple subtractions. The counting method, in contrast, requires seven operations, all additions (not to mention recognizing the nearest multiple of ten in each case).
I guess defenders of this approach could argue that it teaches students the relationship between addition and subtraction, which are complementary. But doesn’t having students “check their work” using the traditional approach accomplish the same end?
(h/t Weasel Zippers)
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