Standard Subtraction with Single Regrouping
This Grade 4 Eureka Math skill teaches students the standard subtraction algorithm with single regrouping. When a digit in the minuend is smaller than the digit in the subtrahend below it, students decompose 1 from the next higher place value and add 10 to the current place. For example, in 352 minus 124, the ones digit 2 is less than 4, so students regroup 1 ten as 10 ones, giving 12 ones minus 4 ones equals 8. This regrouping technique, from Chapter 5 of Eureka Math Grade 4, is the foundational procedure for multi-digit subtraction.
Key Concepts
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.
Common Questions
When do you need to regroup in subtraction?
You regroup when the top digit (minuend) in a column is smaller than the bottom digit (subtrahend). For example, in 352 minus 124, the ones column has 2 minus 4, which requires regrouping.
How do you regroup from the tens to the ones place?
Cross out the tens digit, reduce it by 1, and write 1 ten being added to the ones column, making the ones digit 10 more. In 352, the 5 tens becomes 4 tens and the 2 ones becomes 12 ones.
How does 1 hundred become 10 tens in regrouping?
One hundred equals 10 tens. If you need to borrow from the hundreds, decrease the hundreds digit by 1 and increase the tens digit by 10.
Solve 352 minus 124 step by step using regrouping.
Ones: 2 is less than 4, regroup: 12 minus 4 = 8. Tens: 4 (after regrouping) minus 2 = 2. Hundreds: 3 minus 1 = 2. Answer: 228.
What happens to the tens digit after you regroup from it?
The tens digit decreases by 1 because you moved 1 ten to the ones place. The resulting reduced digit is then subtracted from.