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Make ten to subtract

This understanding involves decomposing a subtrahend so subtraction first reaches a multiple of ten, then completing the remaining subtraction—for example, viewing 32−732-7 as 32−2−5=2532-2-5=25. A number line, ten frame, or place-value representation can show how this partitioning preserves the difference and connects mental subtraction to place-value methods and later subtraction algorithms; the scope is whole numbers within 100, not decimals, fractions, or generalized algebraic strategies.

Detailed Explanation: Make ten to subtract

When you subtract, you can break apart the number you are taking away so you first reach the nearest multiple of ten.

Example: Find 43−843-8.

  1. Start at 4343. To get to 4040, subtract 33:
43−3=4043-3=40
  1. The 88 we need to subtract has 33 used. There are 55 left:
8=3+58=3+5
  1. Subtract the remaining 55:
40−5=3540-5=35

So,

43−8=43−3−5=3543-8=43-3-5=35

You first made a ten, 4040, and then finished subtracting.

Learn by doing: Make ten to subtract

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    Base 10 Blocks - Subtracting - Picture to Answer, With Borrow - Tens and Ones

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