3-Digit Subtraction

3-digit subtraction means taking one three-digit number away from another. A three-digit number is any number from 100 to 999. For example, 725 minus 312. Here, both numbers have three digits, so this is a 3-digit subtraction problem.

3-digit subtraction helps you solve real-life problems like finding change, comparing numbers, or measuring how much more or less something is. We subtract the numbers, one digit at a time, starting from right to left. 

• One place: Subtract the digits in the ones column.
  
   
• Tens place: Subtract the digits in the tens column.
  
   
• Hundreds place: Subtract the digits in the hundreds column.
   

3-digit subtraction with regrouping (also called borrowing) is when we subtract one three-digit number from another, and we borrow from the next place value to help with the subtraction.

While subtracting, if the top digit in a column is smaller than the bottom digit, we need to regroup. This means we borrow from the next higher place value, such as the tens or hundreds place. 

Example: Let’s subtract 512 – 278

  5 1 2
– 2 7 8

Step 1: Ones place → 2 – 8
We can't subtract 8 from 2 because 2 is smaller. So, borrow a ten from the tens place. Since 1 ten equals 10 ones, borrowing a ten gives us 10 more ones to continue the subtraction process. After borrowing, the 1 becomes 0, and the 2 becomes 12.
Now: 12 – 8 = 4

Step 2: Tens place → 0 – 7
Since 1 became 0 after borrowing, we now need to subtract 7 from 0, which is not possible either. So, borrow 1 hundred from 5. Now 5 becomes 4 and 0 becomes 10.
Now: 10 – 7 = 3

Step 3: Hundreds place → 4 – 2 = 2
Final Answer:
512 – 278 = 234
 

3-digit subtraction without regrouping means we are subtracting one 3-digit number from another, and we do not need to borrow at all.
In this case, every digit in the top number is bigger than or equal to the digit below. This allows subtraction without the need for borrowing.

Example: Let’s subtract 864 – 432
   8 6 4
– 4 3 2

Step 1: Subtract the digits in the ones place
4 – 2 = 2

Step 2: Repeat the same for the digits in the tens place

6 – 3 = 3
 

Step 3: Subtract the digits in the hundreds place

8 – 4 = 4

Final Answer:
864 – 432 = 432
 

3-digit subtraction is not something that we do only in math class; we also use it in our daily lives. Here are some real-life examples where we use 3-digit subtraction. 

• Shopping and Money: When we buy something and pay a large amount, we use subtraction to find out the change remaining. For example, let’s say we have $500, and we’ll be spending $275 on toys. We can find out the remaining change by subtracting 275 from 500, which is $225.

• Time and Schedules: Subtraction helps us find how much time has passed or how much time we have left. For example, let’s say our class starts at 9:00 AM and ends at 11:45 AM. We can find the duration of the class by subtracting 9 hours from 11 hours and 45 minutes, which is 2 hours and 45 minutes.

• Travel and Distance: If we're traveling and want to know how many miles are left to reach the destination, we subtract the distance already traveled from the total distance. For example, if a trip is 350 miles long and we’ve already traveled 120 miles, then the remaining distance can be calculated by subtracting 120 from 350, which is 230 miles. 

• Counting and Inventory: In a library, if there are 300 books and 145 are borrowed, we can find the remaining number of books by subtracting 145 from 300, which is 155. So there are 155 books left.
  
  
   
• Classroom Activities: Teachers use subtraction to find out how many students are absent. If there are 460 students in a school and 38 are absent, then 460 – 38 = 422 students are present.