They were just simple review questions. Questions that should be easy to solve, but ones he kept getting wrong. Over and over I had seen him solve problems this way….
$10.00 – $6.43 = $4.43
It is a simple mistake (he is subtracting 3 – 0 instead of 0-3), but any mistake repeated consistently signals a misunderstanding. And misunderstandings requires interventions.
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My first grader, who is doing third-grade math, is familiar with using base 10 blocks to support him in subtracting where regrouping is required. I wanted him to make the connection from this concept to subtracting with money, so out came the base 10 blocks again.
I explained that for today the pennies would equal a cube, longs would equal a dime, flats would equal a dollar, and the cube would equal 10 dollars.
We started off by creating 10 dollars – a cube. I then asked him to take out six dollars. Of course, he replied that he couldn’t do that.
After asking what we could do, he decided to regroup. He also knew that he was going to need to do this for the dimes and pennies so he went ahead and distributed all the base ten blocks. If you have never done this, here is what he did.
- He broke that flat apart and put 10 flats into the dollar space.
- He then took one flat, broke that apart and put 10 longs into the dimes column.
- He then took one long and broke that apart. Once he accomplished that he was able to put 10 cubes into the pennies column.
(For clarification, he did not break it apart literally, he would take a long, place it back into the box, and count out 10 cubes.)
Now the easy part!!! He took away three cubes, four longs, and four flats. The answer was right in front of him, and he excitedly proclaimed it.
Intervention two was very similar to the first one. This time, we just used money and went through the same steps from above.
- Start with 10 dollars
- Traded out the 10 dollar bill for 10 ones.
- Borrowed one dollar and traded it out for 10 dimes.
- Borrowed one dime and traded it our for 10 pennies.
Then he subtracted six ones, four dimes, and three pennies. Once again he found out the answer to $10 – $6.43 is $3.57.
After lots playing with base ten blocks and money, we went to the algorithm. The first few times we worked out the problem, we used the base ten blocks so he could see how the algorithm corresponded with the base cubes. We then proceeded to try out a few problems without any manipulatives!!! When I was convinced he was understanding we moved to some fun task cards.
Intervention 4 – Making Change Task Cards
Finally, we spent the next few days working through the making change task cards and recording our work in our math journals. First, we began with the ones that were very simple and straight forward and progressed to the ones that required numerous steps to complete. Even though my child’s math skills are high, he is still a six-year-old with a very short attention span. When he would choose a making change task card that required multiple steps, we would only do one that day. Many times we would start our math time off with one making change task cards, and then move onto our lesson for the day. I found it a great way to keep this concept fresh in his mind, but allow us to move ahead with our curriculum.
So if you are finding that your child is struggling with making change using an algorithm, I hope these interventions will help you support them. Enjoy the FREE task cards, and You’ve Got This.
Need more ideas for teaching subtraction with regrouping? Check out one of these activities!
Download the free printable HERE.
Other Activities For Making Change:
All About Money by Math Geek Mama
How Much Money Do I Need? by Free Homeschool Deals