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Mathy Mama Justina Straub, M.Ed
I am passionate about helping you become an expert math homework helper!
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10/12/2026

✨Tips for estimating with decimals:

💡We want to round our decimals to the nearest whole number. The TENTHS column is going to control this.

If your student is struggling with this, have them circle the number in the tenths column (the first number after the decimal). Then think about money. Anything less than 50 cents will be closer to the previous whole number. Anything 50 cents or higher will be closer to the next whole number.

💡 How do know if we should round the whole number or leave it as it is? In my second example, how did I know to round the 18 to a 20?

Estimation is not an exact science. The more we round, the more imprecise our answer will be. But we don’t always need precision. I could have chosen to do 9x18 for my estimation, and that would be fine! But it wasn’t needed for the purpose of this problem.

What if the problem was 9x16? I could replace the 16 with 15 and have a great estimate with easier multiplication. And it would be closer to my true answer than 9x20. It would be good to pose this question to kids:
In what real life situations would it be better to calculate 9x15 and when would calculating 9x20 be good enough?

💭 What do you think? Do you use estimation when shopping or comparing prices? Do you do quick calculations in your head, or would you rather pull out your phone and calculate the exact amount? Let me know in the comments!

10/09/2026

Comment “Slider” and I will send you this printable for free!

This idea shows up year after year: we want our kids to understand that the value of a digit increases 10x as it moves to the left on a place value chart. In 5th grade, this idea gets applied to decimals.

📏 I loved the idea of getting kids involved in that movement by making this slider. It can be useful for 3rd-6th grade as this concept continues to be developed.

Pro tip: Print it on cardstock for ease of use. You can laminate the slider to reuse it for each problem, but I’ve also included a page with multiple sliders if laminating isn’t an option for you.

10/07/2026

I'm so grateful for the online community of math teachers, because I've learned something important since I originally recorded this video three years ago. It's a minor change, but it might make a big difference for your kid.

As an Algebra teacher, we live in the world of the abstract - a variable is an unknown quantity, so when we would use the area model to multiply binomials such as
(x + 3)(x - 2),
I would always draw a box and split it into 4 equal squares. I didn't know what x represented, so the size of the squares really did not matter.

I applied the same logic here - the expanded form of 2,741 has four numbers, so I split this rectangle into four equal boxes. It gives us room enough to write in, and I love that.

However, I've since seen some arguments as to why drawing these boxes to scale (at least somewhat) is important.

Moving our students from the concrete, to the representational, to the abstract version of math concepts is so important to help them build math sense. This also applies to the size of the boxes in the area model.

When our students first start the area model, drawing the boxes to scale helps to reinforce the meaning behind what we are doing. A side length of 2,000 should be longer than a side length of 1! As time goes on, we can make those boxes more abstract and start drawing them all the same size, but maybe we shouldn't start there.

Like I said, it's a minor change. What do you think? If you teach 3rd or 4th grade, do you have your students draw their boxes to scale? If you're a parent, would this matter to your student? Let me know in the comments!

09/17/2026

💪🏽 Get ready for a whole bunch of multiplication!

🌟 In 5th grade, we want our students to be pretty fluent with multiplication. Many will be ready to move on to using the standard algorithm, but some will still want to rely on partial products or the area model.

🎥 This is my first in a series of videos that will include a quick review of these three methods, and then a few on multiplying two digit by two digit and three digit by three digit numbers.

🧐 Please feel free to drop any questions in the comments and I’ll be happy to help!

👉🏼 Follow along for help with elementary math topics! Hi, I’m Justina, math teacher and mom of three.
🌟 I want to help you understand the new math methods so you can help your kids with their homework!

09/10/2026

🎉 The ability to choose!!

The more methods that our students understand, the more freedom they have to pick and choose what they think is best for each problem they encounter.

In this problem, when I subtracted 0.7, there are three methods that come to mind. I could have done it the traditional way and regrouped, I could have counted up from 7 to 63, or I could do the way I chose and split it into 0.3 and 0.4. Personally, I like splitting it into two problems, that makes my brain happy.

Which method would you prefer? Subtracting 0.7 in two steps or using a different method that would do it in one step? Let me know in the comments!

👉🏼 Follow along for help with elementary math topics! Hi, I’m Justina, math teacher and mom of three.
🌟 I want to help you understand the new math methods so you can help your kids with their homework!

09/09/2026

🤫 This video isn't for everyone.

By 4th grade, your kid might have a favorite addition method - maybe Adding On really works for their brain, maybe they like the way the Compensation Method lays all of the numbers out, or maybe they are waiting for the day where they can just line everything up and add.

But for those that like the Making Tens method, it is possible to do it with larger numbers! It takes practice with working memory to hold on to the numbers, but all of our kids are capable of learning this method if they want to.

Have you tried adding large numbers mentally? Have you thought about which method your brain naturally uses to do so? Let me know in the comments!

09/08/2026

The BIGGEST mistake kids make while adding decimals is not lining everything up correctly. They have always "right justified" when writing out their addition problems, they carry that over into decimal problems as well.

There are two things you can have your kids do to combat this:
1) Use Color
Have them highlight each place value with matching colors before rewriting the problem - this will remind them to think about place value and put the tenths with the tenths, hundredths with the hundredths, etc.

2) Estimate the Answer
Have them mentally round each addend to the nearest whole number and add. This again makes them think about place value, and in the end if their answer is far off from their estimate they know to double check their work.

They don't even have to round correctly! If they look at this problem and think "3 + 8 = 11, so my answer should be a little more than 11" this will help guide them to setting the problem up correctly.

If you're a teacher, have you found ways to help your students line their decimals up correctly? Please share in the comments, I'd love to hear them!

👉🏼 Follow along for help with elementary math topics! Hi, I’m Justina, math teacher and mom of three.
🌟 I want to help you understand the new math methods so you can help your kids with their homework!

09/02/2026

🤔 Could you add this in your head?

Our students are taught methods that look CRAZY on paper. This leads to so many comments like "Why does this have to be so complicated? Teach them the old fashioned way!"

But what it is hard to convey in a video is that we are teaching them the skills necessary to be able to do these problems mentally. Sure, it takes 2 minutes for me to explain this in a video, but once they have it down, this method can actually be done very quickly in their heads!

Granted, Adding On for numbers in the thousands takes a lot of working memory, but it can be done in less than 10 seconds. Try doing this mentally by lining it up and "carrying the one" - it is much harder.

If your 4th grader stuggles with this method, try doing easier problems with them. Give them some 2-digit plus 2-digit numbers to add together first, then move on to 3-digit numbers, and finally 4-digits.

Up Next: Making Tens and Compensation Methods.

I'll be curious to know which method works best for your brain!

09/01/2026

I love the visual place value blocks give us - physically removing one rod and replacing it 10 unit cubes prepares our kids to "see" what is happening when we teach them the standard algorithm.

By starting with this concrete example, we help our kids develop an understanding of math rather than just memorizing steps to get to an answer.

08/31/2026

🧠 Let’s make those decimals make sense! Using place value blocks is one great way to make adding and subtracting decimals hands on.

🖨️ If you don’t have a set of place value blocks, you can find free printables online! Just print them out (maybe on colored card stock) and cut them out (maybe after laminating them).

They are useful from 1st - 5th grade so a physical set is well worth the investment if you have younger kids.

👉🏼 Follow along for help with elementary math topics! Hi, I’m Justina, math teacher and mom of three.
🌟 I want to help you understand the new math methods so you can help your kids with their homework!

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