In this Grade 5 Pengi Math lesson from Chapter 3, students learn how to add decimals through the thousandths place using regrouping, place-value disks, and the standard vertical addition algorithm. The lesson emphasizes aligning decimal points, annexing zeros as needed, and connecting hands-on models to written procedures for accurate decimal addition.
Section 1
Modeling Decimal Addition with Regrouping
When adding decimals using a place value model, if a column contains 10 or more units (disks), you regroup 10 of those units to form 1 unit in the next larger place value to the left. This is also known as bundling.
Section 2
Relating Place Value Models to Vertical Addition
The standard vertical algorithm for addition is a written representation of adding on a place value chart. Each column in the algorithm corresponds to a place value column, and "carrying over" a digit is the written equivalent of regrouping (bundling) 10 place value disks into one disk of the next larger value.
Section 3
Adding Decimals to the Thousandths
To add decimals, align the decimal points vertically. Add the digits in each place value column, starting from the right, and regroup as needed. Place the decimal point in the sum directly below the decimal points in the numbers being added.
This method for adding decimals is an application of place value. Aligning the decimal points ensures that you are adding digits with the same place value: thousandths to thousandths, hundredths to hundredths, and so on. If numbers have a different number of decimal places, you can add trailing zeros as placeholders. This process is similar to adding whole numbers, with the additional step of placing the decimal point in the final answer.
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Section 1
Modeling Decimal Addition with Regrouping
When adding decimals using a place value model, if a column contains 10 or more units (disks), you regroup 10 of those units to form 1 unit in the next larger place value to the left. This is also known as bundling.
Section 2
Relating Place Value Models to Vertical Addition
The standard vertical algorithm for addition is a written representation of adding on a place value chart. Each column in the algorithm corresponds to a place value column, and "carrying over" a digit is the written equivalent of regrouping (bundling) 10 place value disks into one disk of the next larger value.
Section 3
Adding Decimals to the Thousandths
To add decimals, align the decimal points vertically. Add the digits in each place value column, starting from the right, and regroup as needed. Place the decimal point in the sum directly below the decimal points in the numbers being added.
This method for adding decimals is an application of place value. Aligning the decimal points ensures that you are adding digits with the same place value: thousandths to thousandths, hundredths to hundredths, and so on. If numbers have a different number of decimal places, you can add trailing zeros as placeholders. This process is similar to adding whole numbers, with the additional step of placing the decimal point in the final answer.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter