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2nd grade math · Unit 3: Adding and subtracting within 100

Count up to subtract

What this lesson shows

62 − 39: from 39, jump 1 to 40, 20 to 60, and 2 to 62. That is 23.

The worked example

The lesson works this one step by step: 62 − 39 = □. Then your kid tries one like it on paper.

The steps

  1. Start at the smaller number
  2. Jump to the next ten
  3. Jump the tens, then the rest
  4. Add the jumps

Helping at home

Start at the smaller number on a line. Jump to the next ten, then by tens, then to the bigger number. Add the jumps: that is how far apart they are.

If your kid gets stuck

Start at the smaller number.

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 2.NBT.B.5
    Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
  • Common Core 2.MD.B.6
    Represent whole numbers as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, ..., and represent whole-number sums and differences within 100 on a number line diagram.
Matches a standard in all 50 states and DCSee each state's code

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