Double Digit Addition Strategies

This year, my school has decided to put a huge emphasis on what it means to have “number sense” in the primary grades. In order for this to happen, we had to put an emphasis on a few key questions:

  • What does it mean to be fluent?
  • How do we assess number sense?
  • What are the “wish list” strategies that we want kids to come in with at each grade level?

No, we don’t have the answers to all of these yet, but we do have a strong(er) grasp on what we DON’T want to do with our kids.

In first grade – we did NOT want to teach them algorithms that were only going to hinder their understanding as they progressed through the grades. So, as one of my teammates said, “We don’t stack, we go flat!”

Do you remember being taught to start with the ones, carry your tens, etc. etc.? Me, too! But, thanks to Common Core Standards, we are moving away from some of the methods you and I were taught as kids.

My team…and every grade up until 4th grade in my building now…is no longer doing those algorithms. Instead, we have an emphasis on basic number sense and mental strategies.

To do this with double digit addition, your kiddos HAVE to have some strong understanding of place value. This is why we started our double digit addition unit with reviewing place value. We use a combination of manipulatives for this but my favorite is 10s and 1s cards.

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We also extend this with arrow cards so kids can begin to get exposed to expanded form. This lets them hear the language that 94 is really 90 + 4 or 9 tens and 4 ones.

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Once students are ready, I move on to double digit addition with manipulatives.

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I prefer connecting cubes to the base 10 blocks because it lets my kids actually BUILD the stick of ten. Sure, it takes a little longer, but this makes all of the difference for some kids. Some kids struggle with understanding that one longer stick of base 10 blocks is truly 10 cubes. So, by building the stick of ten themselves, their understanding is made more concrete. Using the mat in my unit, we write the number sentence at the top before we build the number. We make sure everyone agrees on the number of tens and ones and then…we BUILD!  We grab the ones and drag them to the bottom. Next, grab the tens and drag them to the bottom. Finally, add ’em up!

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Next, we move on to DRAWING our tens and ones. I call these “swooshes” and “thunks.” 🙂 Make it quick and paperless by pulling out some dominoes with your whiteboards. You might need to keep an eye out for those tricky problems that require regrouping, though!

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Open Number Lines are also a great strategy! Use BIG humps for the tens, and little bitty baby humps for the ones. I love to tell them this is the strategy I use in my brain all of the time. It makes them feel grown-up!

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Our last strategy is decomposing the numbers. We relate this back to the expanded form with arrow cards by breaking numbers down into the hunks of tens and ones. In the example above, you can see she broke 46 down to 40 + 6 and 62 down to 60 +2. Then, as usual, we add the ones first and then the tens.

Once kids have their tools in their tool belt, they’re ready to venture off on their own!

Get all of this, practice pages and games, and videos of me teaching the strategies in my newly updated Double Digit Addition packet in my TeachersPayTeachers Store!

Click the picture below to be taken to the packet!

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How do you introduce double digit addition? Comment below!

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