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➕ Adding and Subtracting Within 100

Build strategies for adding and subtracting up to 100 — making ten, breaking numbers apart, and using place value — until the small facts feel automatic.

3
lessons
~30 min
to learn
🔢 Math
subject
Ages 6–12
level
Start the course →

What you’ll learn

  1. Facts You Know by HeartRecall addition and subtraction facts within 10 quickly, using doubles and counting on.Small facts within 10 are your quick tools. Doubles like 4 + 4 = 8 are fast, and near-doubles build on them. When facts within 10 pop up instantly, your brain is free to handle the trickier steps of bigger problems.
  2. Making Ten Within 20Add and subtract within 20 by making ten or decomposing to ten, like 8 + 6 = 14 and 13 - 4 = 9.Adding to ten is easy, so build a ten first. For 8 + 6, split the 6 into 2 and 4: 8 + 2 = 10, then 10 + 4 = 14. Subtraction works the same in reverse: for 13 - 4, hop back to 10 first, then take the rest.
  3. Reaching Within 100Add within 100 using place value, like 46 + 7 = 53 and 38 + 40 = 78.For 46 + 7, step up to the next ten first: 46 + 4 = 50, then 50 + 3 = 53. Adding a whole ten, like 38 + 40, changes only the tens digit. Keeping tens with tens and ones with ones lets you add neatly up to 100.

Questions this course answers

For 13 - 4, breaking to ten means you first do...

Hop back to the friendly ten first: 13 - 3 = 10, then 10 - 1 = 9.

When you add a whole ten to a number, which digit changes?

Adding a ten changes only the tens digit; the ones stay the same.

Grounded in trusted sources

  • Khan Academy Kids
  • PBS Kids — early math
  • NAEYC — early math learning
  • National Council of Teachers of Mathematics (NCTM)

Every Wunder lesson is built from real, reputable sources — never invented.

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