In this Grade 4 Pengi Math lesson, students learn to fluently subtract multi-digit whole numbers using the standard subtraction algorithm. The lesson focuses on proper digit alignment and systematic decomposition, commonly known as borrowing, to solve subtraction problems accurately. Part of Chapter 2 on algorithms and fluency, this lesson builds the foundational skills needed for multi-step problem solving.
Section 1
Standard Subtraction with Single Regrouping
When subtracting vertically, if a digit in the top number (minuend) is smaller than the digit below it (subtrahend), you must regroup. To regroup, you decompose 1 from the next higher place value to the left and add 10 to the current place value. For example, 1 hundred becomes 10 tens, or 1 ten becomes 10 ones.
Section 2
Subtracting with Multiple Regroupings
To subtract multi-digit numbers, align them by place value and subtract column by column from right to left. If a top digit is smaller than the bottom digit, decompose 1 unit from the place to the left, which is equivalent to adding 10 to the current place. This process may need to be repeated multiple times, including across places with a value of zero.
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Section 1
Standard Subtraction with Single Regrouping
When subtracting vertically, if a digit in the top number (minuend) is smaller than the digit below it (subtrahend), you must regroup. To regroup, you decompose 1 from the next higher place value to the left and add 10 to the current place value. For example, 1 hundred becomes 10 tens, or 1 ten becomes 10 ones.
Section 2
Subtracting with Multiple Regroupings
To subtract multi-digit numbers, align them by place value and subtract column by column from right to left. If a top digit is smaller than the bottom digit, decompose 1 unit from the place to the left, which is equivalent to adding 10 to the current place. This process may need to be repeated multiple times, including across places with a value of zero.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter