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Adding and Subtracting within 100

Aligned to 2.NBT.B.5 — Common Core State Standards for Mathematics.

What this lesson teaches

Add and subtract two-digit numbers by working with tens and ones separately, regrouping (carrying or borrowing) when needed.

Worked example

47 + 38: add ones 7+8=15 (write 5, carry 1 ten); add tens 4+3+1=8. Answer: 85.

Practice questions

  1. Solve 56 + 27.
  2. Solve 63 − 28.
  3. Why do we 'carry' when the ones add to more than 9?

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En español

Suma y resta hasta 100

Suma y resta números de dos dígitos trabajando por separado con las decenas y las unidades, reagrupando (llevando o pidiendo prestado) cuando sea necesario.

Ejemplo: 47 + 38: suma las unidades 7+8=15 (escribe 5 y lleva 1 decena); suma las decenas 4+3+1=8. Resultado: 85.

More Number & Operations in Base Ten lessons

Hundreds, Tens, and Ones2.NBT.A.1Counting and Skip-Counting2.NBT.A.2Reading and Writing Numbers to 10002.NBT.A.3Comparing Three-Digit Numbers2.NBT.A.4Adding Several Two-Digit Numbers2.NBT.B.6Adding and Subtracting within 10002.NBT.B.7

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