### 5th Grade Place Value and Decimals: From Thousandths to Billions

5th grade Math Unit 2 involves place value from thousandths to billions, comparing and ordering numbers from thousandths to billions, and finally, adding and subtracting decimals.

The all encompassing, end of unit assessment can be downloaded in .doc format HERE to get you started.

These concepts are important to future success in math, and are taught in three parts so that the concepts scaffold onto one another as we go. This unit comes after a large numbers and operations unit that we started the year with, one in which students identified factors and multiples, worked with prime factorization, and finally refined skills in multiplication and division.

The unit is split into its three parts here, with all necessary exams and paperwork attached:

Unit 2.1: PLACE VALUE FROM THOUSANDTHS TO BILLIONS

It's important that students have an understanding of very large and very small numbers in the 5th grade. So we start by working on place value. Place value is a good place to start because it comes down to practice, repetition, and memorization of the place values.

The PDSA that accompanies unit 2.1 can be downloaded HERE.
The Unit 2.1 Assessment can be downloaded HERE. (I should mention right here that most of the assessments I have are also available in Spanish. Just let me know if you're interested).

By applying backwards design to this portion of Unit 2, the assessment shows a need for knowledge in: expanded notation, written notation, standard notation, and place value.

Activities to meet these needs are listed below:

First, I highly recommend a great activity called Place Value Cups. I originally came across this activity on a blog titled Look+Listen=Learn. By making these cups, students are given multiple opportunities to practice place value and expanded notation at the same time. It's a great activity, and I'm excited to see the difference it can make with students who struggle with this concept.

Teaching place value and the different notations is actually quite different than a lot of mathematical concepts. By this age, it should be more refinement and scaffolding than outright teaching. Let's be honest, if a child reaches 5th grade and has no understanding of place value, they've probably never been instructed before, or had some flat out awful teachers in the past, because it's integral to 3rd and 4th grades. I've found that students benefit more from practice practice practice than anything else. So while using the place value cups, I also refine the concept of how to say numbers.

Saying numbers aloud, especially larger numbers and numbers with decimals in them, can be daunting for the struggling math student. When I say "saying numbers aloud," I'm also teaching expanded notation. I like to rely on comma naming to give students a chance to know how to say numbers possibly before they conceptually understand big numbers (millions and beyond).

I teach students that the first comma is called thousand, the second is called million, and the third is called billion. We practice this in class. Then, we practice saying numbers with comma names. The great thing about this is that students never have to actually say a number larger than hundreds. Here's an example:

324,783,013.... The student would first say three hundred twenty four. This is simple, it's a concept that has been mastered by the vast majority of 5th graders years ago. Then it's a matter of naming that comma. It's the third comma we're looking at, and its name is billion. So, three hundred twenty four billion... Then the student would continue on... seven hundred eighty three, this time it's the second comma, million... seven hundred eighty three mission... thirteen. And that's the end of that. It really helps students understand and be able to say numbers, which we then build on with expanded notation. Expanded notation is fairly straight forward. It will also be covered in the resources below:

Here's a few resources to get you started:

Unit 2.2: COMPARING AND ORDERING DECIMALS

After we have taught place value to thousandths (and billions), we move on to ordering decimals, and comparing decimals with <,>,= statements.

The PDSA for Unit 2.2 can be accessed HERE.
The assessment for Unit 2.2 can be accessed HERE.

By using the same method of backwards design, starting with the 2.2 assessment, we see that in this particular cycle of the lesson, students will be learning how to apply less than, greater than, and equal to statements to decimals, and will learn how to order large numbers with decimals (and simply large numbers is also acceptable here) either from greatest to least or least to greatest. Finally, it's important to apply these skills to word problems. So here we go:

• Head off to Khan Academy for his lesson on Comparing Decimals. Khan Academy is great, because he teaches through video, and offers various practice problem sets. Plus, he's got TONS of stuff.
• Fruit Shoot Comparing Decimals Game: An interactive game for students to play.
• I like for my students to practice ordering numbers on hanging number lines. It's a simple concept involving string and folded pieces of paper (or note cards).

• This document, titled Gap Closing, has some great activities to fit this unit of study, particularly comparing and ordering decimals.
• This pdf document includes a small chart I have my students make so they can begin to understand conceptually how and why they compare numbers, and what it actually means, in terms of place value, when one number is larger than another.
• Finally, a refresher on inequality symbols (if your students don't know this, they need to know this!)
UNIT 2.3: ADDING AND SUBTRACTING DECIMALS

Finally we end this unit with a cycle on adding and subtracting decimals. The concept is straight forward, and quite simply involves lining up the numbers to be added or subtracted by the decimal point.

The PDSA for cycle Unit 2.3 can be downloaded HERE.
The Unit 2.3 assessment can be downloaded HERE. If you like to save time, as my grade level team does, we don't use this assessment, instead, we simply score the final page (the adding and subtracting decimals page) twice, once as part of the unit score, and once for a unit 2.3 score.

Just remember, the concept of adding and subtracting decimals is quite simple. It all comes down to lining up the decimal, regardless of how huge one number might be and how small the other might be. Your students also might think about using zeros as placeholders when doing this!