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Progression in written methods for subtraction

Progression in written methods for subtraction. NNS recommendations. Stage 1: counting up from the smaller to the larger number. I can find 84 - 56. Watch! 56 + 4 + 20 + 4 = 84. So 84 – 56 = 28. Stage 2: compensation. Here we take too much then add back.

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Progression in written methods for subtraction

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  1. Progression in written methods for subtraction NNS recommendations

  2. Stage 1: counting up from the smaller to the larger number I can find 84 - 56. Watch! 56 + 4 + 20 + 4 = 84. So 84 – 56 = 28.

  3. Stage 2: compensation Here we take too much then add back. 84 - 56 is the same as 84 – 60 + 4 which is 24 + 4 = 28!

  4. 563 – 241 = 500 + 60 + 3 - 200 + 40 + 1 300 + 20 + 2 So 563 – 241 = 322 Stage 3: use of the expanded subtraction algorithm (no decomposition required) This stage is the beginning of the standard algorithm but in a much expanded format. As no decomposition is required, the calculation can be done left to right. I understand how this method works!

  5. 566 – 278 = 500 + 60 + 6 = 400 + 160 + 6 - 200 + 70 + 8 - 200 + 70 + 8 = 400 + 150 +16 - 200 + 70 + 8 200 + 80 + 8 = 288 Stage 4: use of the expanded subtraction algorithm (decomposition required) This is a bit more difficult. I have to exchange 1 hundred for 10 tens and 1 ten for 10 units!

  6. Stage 5: standard method The standard contracted algorithm is used using decomposition where necessary. I understand how to use this method because really it is the same as the last method we used! 566 – 278 = 51616 - 2 7 8 2 8 8

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