## Unit 6- Foundations of Numbers up to 99

This unit bundles student expectations that address the understanding of whole numbers up to 99, comparing numbers using place value, and ordering these numbers using

an open number line.

Prior to this unit, in Unit 04, students were introduced to the base-10 place value system as they explored whole numbers up to 20. Students composed and decomposed numbers through 20 using concrete objects, pictorial models, and numerical representations. In addition, students used place value relationships and tools, such as a hundreds chart, as they generated numbers more or less than a given number. Students compared whole numbers up to 20 using comparison symbols and were introduced to using place value and open number lines to order whole numbers.

During this unit, students extend their knowledge of the base-10 number system by using objects and manipulatives to form multiple groups of tens and ones up to 99.

Students compose and decompose numbers through 99 as a sum of so many tens and so many ones using concrete objects (e.g., proportional objects such as base-10 blocks), pictorial models (e.g., base-10 representations with place value charts), and numerical representations (e.g., expanded form and standard form). Students use place value relationships in order to generate numbers that are more or less than a given number using tools such as a hundreds chart and/or base-10 blocks. Students compare whole numbers up to 99 and represent the comparison using comparative language and symbols. Students use open number lines to represent the order of numbers.

## Linking Cubes, Base Ten Blocks, Place Value Disks, OH MY!

When starting to think about what manipulative to use for this unit, we need to think about what is developmentally appropriate and also take into account the specificity of the TEK.

1.2B states that students will use concrete and pictorial models to compose and decompose numbers up to 120(which in this unit we are ONLY going to 99) in more than one way as so many hundreds, so many tens, and so many ones. In the specificity it says to use concrete proportional models (linking cubes, base ten, and bundles of sticks).

Knowing all of this research says that developmentally 1st graders are not ready for base ten blocks so linking cubes are the best way to do place value. Van de Walle recommends groupable manipulatives prior to using traditional base-10 blocks, because they can physically be joined together and broken apart. Traditional base-10 blocks are actually a little more abstract because, for example, you can’t break the tens rod apart into ones–you have to trade it for ones.

That being said we have to also get kids ready for 2nd grade and the expectation that they will have to go from only doing numbers to 120 to 1,200. Not to mention they also have to use place value disks and are tested on those skills. So if we never expose them to base ten is that the best?

So here is what I recommend, review numbers 0-20 with linking cubes and then make the connection to base ten blocks. We will also make sure that we are taking students through the whole concrete-representational-abstract process during this unit.

place value math song: ones, tens, hundreds
Teacher Tipster (Place Value Song)