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We were standing in the Valentine’s Candy isle, and I was trying to figure out the cheapest way to purchase enough candy for all four of my kiddos to put on their Valentine’s Cards. One package of red and silver hearts wasn’t considerate enough to place the amount on the package, and I found myself reading the serving label.

The serving info informed me that 1 serving was three pieces, and there were 12 servings in the package. At this point, I turned to my recently turned seven-year-old and asked him how many chocolate hearts were filling the bag.

“Well, I know that 12 x 2 = 24!”

“Good,” I encouraged. “Now what?”

“Well I’ll add ten, that is 34 and add another 2 that is …..” he paused and then shouted a little louder than he should have for a store and said, “36!!!!”

I smiled, and couldn’t help but throw in a division problem….. since that is actually what we are working on right now…….so if each of you needs twenty pieces of candy, can two of you use this bag.

He thought, for just a second and then proclaimed that I couldn’t.

Adding and Subtracting by 10

Did you notice that when my seven year old was asked to do some mental math, he added by 10 first? It is a great strategy, that makes adding mental possible, even when you are working with two digit numbers.

We spend enormous amounts of time on our number chart, moving up and down by 10’s and 1’s until this became second nature to him. But sometimes it is fun to add in practice in other ways!

And these number puzzles are a perfect way to work on logic and adding and subtracting by 10.

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Prep Work

  1. Simply print out the number puzzles and cards
  2. Cut out the cards
  3. Provide glue


To make this a center to be done over and over…

  1. Print everything out on card stock and laminate
  2. Place magnetic strips on the back of the cards
  3. Grab a cookie tray

How to use Adding and Subtracting by 10 Center

Crazy Squares is similar to Suduko puzzles. You must fill in the squares so that the same number is not in any row, column, or large square.

We began by figuring out the four numbers needed. Some number are on the board, and others we had to solve some of the problems to figure out.

Once we knew what four numbers would help us solve the problem, we moved on to figuring out where the expressions were going to go.

We started on a row that only had one empty space, and then figured out what number was missing. Once we had placed the correct expression, we started looking for another row, column or square that just had one missing square.

Sometimes it was easy to find a place that was missing one square, other times we would have a row with two empty spots and some reasoning would come into play. By studying the columns and square that the two empty spaces were in, we would find a duplicate number. Seeing that number would help us deduct where we needed to place the next number.

There was a ton of adding and subtracting by 10 with this activity and a lot of logic and reasoning used. So next time we happen to be standing in a store aisle looking at servings, I’m sure my little man will be able to help me figure out what we need to purchase.

You’ve Got This

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Get the Crazy Squares plus Bone Puzzles and Game to help your students practice adding and subtracting by ten at TpT.