Adding and Decomposing to 20 Worksheet
This adding and decomposing to 20 worksheet gives 1st graders double ten frames for building teen sums and reading them back as a ten and some ones. Answer key included, so practice checks itself in seconds.
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About this resource
Description
Adding and decomposing to 20 is the moment first graders stop counting every object and start seeing a teen number as a ten and some ones. When a child knows that 10 and 6 make 16, and that 16 can be pulled back apart into 10 and 6, addition within 20 becomes fast and flexible instead of slow and one-by-one. This adding and decomposing to 20 worksheet builds that understanding with double ten frames, the model most first-grade classrooms already use, so the picture on the page matches the picture in your student’s head.
This printable 1st grade addition worksheet moves from drawing to reading to applying. In Part A your student writes each sum and then fills the two ten frames to match, filling the first frame completely before starting the second. In Part B the frames are already filled with dots, so the thinking runs the other way: count the dots and finish the addition sentence. Part C ends with a short word problem about Steven and his hops, where the same ten-and-ones strategy solves a real situation. Print it as morning work, a guided-math station, homework, or a quick check before an addition assessment.
What’s Included
- 1 print-ready PDF worksheet
- Answer key
- 4 write-the-sum and fill-the-ten-frame problems
- 2 read-the-ten-frames addition sentences
- 1 illustrated addition word problem
Three things make this resource work in a first-grade classroom. First, the double ten frame gives every teen number the same shape, so students see that 13, 16 and 19 are all “one full ten and a few more” rather than nineteen separate marks. Second, this adding and decomposing to 20 worksheet asks students to move in both directions — build the model from an equation, then write the equation from a model — which is the difference between memorizing an answer and understanding a number. Third, the word problem puts the skill in a story, so students practice deciding which operation to use, not just how to compute it.
Teachers and parents can stretch this skill well past the page. Hand your student a pair of paper ten frames and a cup of counters and call out teen numbers to build and take apart. Play a quick partner game where one child covers part of a filled frame and the other names the missing ones. Use snack time — ten crackers on one napkin and a few more on another — to ask “how many in all?” Sing along with an addition song in the car, and keep a small stack of these sheets ready for early finishers or a five-minute warm-up.
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