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1st grade math · Unit 1: Adding and subtracting within 20

Which addition helps?

What this lesson shows

Fixes a mistake

For 11 − 4, 4 + ? = 11 helps. 11 + ? = 4 does not.

The worked example

The lesson works this one step by step: 11 − 4 = □. Then your kid tries one like it on paper.

The steps

  1. The big number is the whole
  2. Start with the part
  3. Part plus what makes the whole?

Helping at home

Start the addition with the number you take away: it is a part. Ask what plus it makes the big number. The big number never goes first.

If your kid gets stuck

Start with the number you take away.

Watch it with Lux

With Lux, this lesson is a narrated video and a printed page your kid works on. Then Lux helps with the same math on their own worksheet, one question at a time.

See how Lux works

Standards

  • Common Core 1.OA.B.4
    Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.
Matches standards in 44 statesSee each state's code

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