Subtraction strategies, part 1: Use known subtraction facts

We can solve 23 − 8 and 93 − 8 (and 63 − 8 etc.) by our knowledge of the basic subtraction fact that 13 − 8 = 5. Think of it this way: in 13 − 8, the answer goes "down" to the previous ten, and ends in 5. It works the same way for 63 − 8, for example: the answer is in the previous ten (in the 50s) and ends in 5.

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Subtraction strategies, part 2

Math Mammoth Grade 3 curriculum

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