Video: Finding One Less Than a Known Double as a Strategy to Add

Michael was asked to solve 6 + 5. He wrote, 6 + 5 = 11 because 6 + 6 = 12 and 12 − 1 = 11. Is his solution correct?

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Video Transcript

Michael was asked to solve six plus five. He wrote six plus five equals 11 because six plus six equals 12 and 12 take away one equals 11. Is his solution correct?

Michael is trying to solve six plus five. He’s using a doubles fact to help him. The doubles fact that he’s using is six plus six is 12 or double six is 12. This model shows double six. Does double six equal 12? We could count on twos to help check: two, four, six, eight, 10, 12. Double six is 12.

Michael also says that six plus five is 11 because six minus one is five. He’s correct. Six minus one is five. Six and five is 11. Or 12 take away one is 11. So his solution is correct. So the answer to the question is yes, his solution is correct.

Michael said that six plus five is 11 because six plus six equals 12 and 12 take away one is 11. We proved he was correct, using our counters to help us.

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