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Make ten to add

Making ten to add means decomposing one addend so part combines with the other addend to form 10, or, for two-digit numbers, the next multiple of ten—for example, 8 + 5 = 8 + 2 + 3 = 13 and 27 + 6 = 27 + 3 + 3 = 33. This reasoning connects addition to place value, the associative and commutative properties, and flexible mental calculation within 100; it does not include generalized algorithms for larger numbers.

Detailed Explanation: Make ten to add

To make ten, break apart one addend so that part of it joins the other addend to make 1010.

Example: Find 8+58+5.

  1. Ask, “How many more does 88 need to make 1010?”
    It needs 22.

  2. Break 55 into 22 and 33:

5=2+35=2+3
  1. Add the part that makes ten:
8+2=108+2=10
  1. Add the leftover part:
10+3=1310+3=13

So,

8+5=8+2+3=10+3=138+5=8+2+3=10+3=\boxed{13}

Learn by doing: Make ten to add

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    Ten Groups - Add, With Carry, Less than 20

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