1 / 6

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.

matt
Download Presentation

Progression in written methods for subtraction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related