Understanding Subtraction within 1000
What You Already Know: You can subtract two-digit numbers and understand place value with hundreds, tens, and ones!
Part 1: Mental Subtraction with Round Numbers
When we subtract round numbers (like 100, 200, or 50), we can do it in our heads!
Subtracting Hundreds
When you subtract 100, 200, or 300, just subtract from the hundreds place:
- 567 - 100 = 467 (5 hundreds minus 1 hundred = 4 hundreds)
- 834 - 200 = 634 (8 hundreds minus 2 hundreds = 6 hundreds)
- 750 - 300 = 450 (7 hundreds minus 3 hundreds = 4 hundreds)
Subtracting Tens
When you subtract 10, 20, 30, etc., just subtract from the tens place:
- 456 - 30 = 426 (5 tens minus 3 tens = 2 tens)
- 689 - 50 = 639 (8 tens minus 5 tens = 3 tens)
Subtracting Ones
When you subtract small numbers, just subtract from the ones place:
- 478 - 5 = 473 (8 ones minus 5 ones = 3 ones)
- 893 - 2 = 891 (3 ones minus 2 ones = 1 one)
Part 2: Written Subtraction WITHOUT Regrouping
What does "without regrouping" mean? It means each digit on top is bigger than or equal to the digit below it. We can subtract each place directly!
Example: 789 - 456
789 - 456 ------- 333
Step by step:
- Ones: 9 - 6 = 3
- Tens: 8 - 5 = 3
- Hundreds: 7 - 4 = 3