## Base 10 blocks are a go to representation for place value. They are also easy to implement for addition or subtraction with place. With a group model, they are useful for multiplication and division. It is harder to model multiplication of multi-digit numbers with regrouping. This post presents a Google Jamboard with base 10 blocks on a scaffolded chart to provide such a model.

### Overview

The structure aligns with the group representation of multiplication. The # of items in each group is presented first as this aligns with unit rate and slope problems.

### Steps

The steps are listed in each photo in the gallery below. Here is a Youtube and FB Reel video showing the steps.

Here is a link to the Jamboard. You must make a copy to access it.

## Tenths vs Tens…Hundredths vs Hundreds. Problematic for many students. I believe this is a conceptual problem. This post provides an approach to unpack the concepts through money in a scaffolded handout.

### Overview

Money is likely prior knowledge for many if not most students, and is a relevant context. This handout attempts to leverage interest or knowledge of money to unpack decimal place values. In the first page, the concept of “tenth” is addressed with dimes as 1/10 of a dollar. Similarly, “hundredth” is addressed with pennies as 1/100 of a dollar. A key point to consider is that US monetary system base unit is a dollar. More on that in the other pages.

### Hundreds to Hundredths

The handout aligns each place value with the appropriate currency. This is followed by writing each number in numeric form and then word form with the place value table as a guide. To enhance the word part, you can highlight the each place value in money, digit, and word in the same color (e.g., the “2” in yellow).

Also, note the shading. The dollar as the base unit is in the center and shaded the darkest. The tens and tenths are shaded the same as they are a factor of 10 from ones. (I don’t reference the term with students.) Same for hundreds and hundredths.

### Thousandths

here is a link to the handout.

## Students who struggle with number sense, such as place value, struggle with subsequent math content. Connecting place value to prior knowledge or an area of interest can be an entry point to making place value accessible. This post shows how a student interest (horses) can be leveraged to present place value in a more accessible fashion.

The student likes horseback riding. This can be useful to make the concept relative (10 horses live in a barn) and engaging. Here is a YouTube video and a FB Reel showing how this works. The key is 10 horses can “enter” the barn and disappear.

The Jamboard has a slide with a Legos version. This allows a nice transition from using actual Legos as the 1×1 blocks can connected to make a 10.

Here is a link to the Jamboard. You have to make a copy to use.

## Multiplying and Carrying a Tens Digit

Carrying the TENS digit in a multiplication problem is a sticking point for many students. To address this, I use a task analysis approach to zero in on the step of identifying the product for the ONES as a prelude to carrying.

In the example below, 5 and 4 are in the ONES place and the product is 20. The task analysis steps involved:

• compute the product
• identify the digits in the product
• identify the digit in the ONES
• identify the digit in the TENS
• Understand that the TENS digit must be carried to the TENS column

By creating a place holder for the product and scaffolding it to differentiate between the TENS and the ONES, the student can visualize the product. This reduces the demand placed on working memory. Once mastery with the place holder is demonstrated, it can be faded (and used as necessary as part of corrective feedback).

NOTE: I started this mini-lesson for a student with ADHD by having him warm up with problems without carrying. Also, extra line below the 60 and 20 are used for multiplying by 2 digit numbers (next in the sequence).

Here is a post on how I use color coding to unpack the multiplication by 2-digit factors.

## Adding ones digits in 2 digit numbers with carrying

### First, I target the step of identifying the ONES and TENS place in the 2 digit sum in the ONES column (below it is 12). In a scaffolded handout I create a box to for the sum with the ONES and TENS separated. At first I give the sum and simply have the student carry the one. ### Then I have the student find the sum and write it in the box (14 below). Once mastered I have the student write the sum and carry the 1. ### Finally, the student attempts to add without the scaffolding. I continue with color but then fade it. 