Section 1
Using Compensation for Subtraction
Property
To mentally calculate a difference like , you can change the subtrahend () to a nearby, easier number (). Then, subtract from and adjust the result by adding the difference between and .
In this Grade 5 lesson from Pengi Math, students learn mental subtraction strategies for decimals, including compensation, place-value decomposition, and number line representation. The lesson builds flexible thinking by connecting place value to step-by-step subtraction and teaches students to estimate differences to check for reasonableness.
Section 1
Using Compensation for Subtraction
To mentally calculate a difference like , you can change the subtrahend () to a nearby, easier number (). Then, subtract from and adjust the result by adding the difference between and .
Section 2
Using the Partial Differences Method
To subtract using partial differences, break the second number into its place value parts (e.g., ones, tenths, hundredths). Then, subtract each part one at a time from the first number. For a problem like , the process is:
Section 3
Modeling Decimal Subtraction on a Number Line
To subtract decimals on a number line, start at the minuend (the first number) and move to the left. The total distance moved is the value of the subtrahend (the second number). The final position on the number line is the difference.
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Section 1
Using Compensation for Subtraction
To mentally calculate a difference like , you can change the subtrahend () to a nearby, easier number (). Then, subtract from and adjust the result by adding the difference between and .
Section 2
Using the Partial Differences Method
To subtract using partial differences, break the second number into its place value parts (e.g., ones, tenths, hundredths). Then, subtract each part one at a time from the first number. For a problem like , the process is:
Section 3
Modeling Decimal Subtraction on a Number Line
To subtract decimals on a number line, start at the minuend (the first number) and move to the left. The total distance moved is the value of the subtrahend (the second number). The final position on the number line is the difference.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter