Learning to add and subtract by 10 is an essential skill for mental math. This adding by 10 activity is a fun and challenging way to practice this skill.

### The free printable can be found at the END of this post. Click on the blue “get your free printable here” button.

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 mentally 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.

*This post contains affiliate links to Amazon products

### Prep Work

- Simply print out the number puzzles and cards
- Cut out the cards
- Provide glue

OR

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

- Print everything out on card stock and laminate
- Place magnetic strips on the back of the cards
- Grab a cookie tray

Good Cook 13 Inch x 9 Inch Cookie SheetMagnefic! Magnetic Squares, 1 tape sheet of 70 magnetic squares (each 20x20x2mm), magnet on one side, self adhesive on the other side. Perfect for fridge organisation, DIY art project, vision board

## How to use Adding 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.

#### A little Reasoning

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.

Just as in Suduko, you have to study rows, columns, and the large square to come up with an answer.

In the example above, I know that 72 will have to go next to the 39 in the top left square. So in the bottom left square 72 will have to be between the 39 and 75.

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

### You may also be interested in….

Or get all four adding and subtracting by 10 activities in one easy download.

This is a subscriber freebie. If you are already a subscriber, check the most recent email for the latest password. If you aren’t a subscriber, sign up below and the password will be provided in the first email you receive. You will also get $2 off to use the You’ve Got This Store.

You’ll find it under the Adding and Subtracting section!