Rule of Subtraction For 3 Digit Numbers

The rule for subtracting three-digit numbers is similar to subtracting smaller numbers but requires careful attention to borrowing when needed. Here’s a step-by-step guide:

Step 1: Align the Numbers

• Write the two numbers one under the other, aligning them by their place values (hundreds, tens, and ones).
• Make sure the digits in the ones place, tens place, and hundreds place are directly above or below each other.

Step 2: Start Subtracting from the Right

• Begin with the Ones Column: Subtract the digit in the bottom number’s ones place from the digit in the top number’s ones place.
  • If the top digit is smaller than the bottom digit, borrow 1 from the tens place.
• Move to the Tens Column: Subtract the digit in the bottom number’s tens place from the digit in the top number’s tens place.
  • If we borrowed 1 from the tens place in the ones column, subtract 1 from the top digit before subtracting the bottom digit.
  • If the top digit is smaller than the bottom digit, borrow 1 from the hundreds place.
• Finish with the Hundreds Column: Subtract the digit in the bottom number’s hundreds place from the digit in the top number’s hundreds place.
  • If we borrowed 1 from the hundreds place in the tens column, subtract 1 from the top digit before subtracting the bottom digit.

Step 3: Write Down the Result

• After we have subtracted all the columns, write down the final result, which is the difference between the two three-digit numbers.

Example:

Let’s subtract 369 from 482.

  482
− 369
------

1. Ones place: 2 − 9. Since 2 is less than 9, borrow 1 from the tens place. This makes the 2 a 12.
   • Now, 12 − 9 = 3. Write down 3 in the ones place.
   • The tens place now has 7 (since we borrowed 1 from it).
2. Tens place: 7 − 6 = 1. Write down 1 in the tens place.
3. Hundreds place: 4 − 3 = 1. Write down 1 in the hundreds place.

So, the difference is 113.

  482
− 369
------
  113

Borrowing Process:

• Borrowing: If the digit in the top number is smaller than the corresponding digit in the bottom number, we need to borrow from the next left place value. Borrowing decreases the digit in the next column by 1 and increases the digit we are subtracting by 10.

This is the basic rule of subtraction for three-digit numbers.