3-Digit Subtraction

3-digit subtraction involves subtracting one three-digit number from another. A three-digit number ranges from 100 to 999. For example, subtracting 312 from 725.

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.

The process involves subtracting each digit, starting from the rightmost (ones place), then the tens place, and finally the hundreds place.

3-digit subtraction with regrouping, also known as borrowing, happens when we subtract one three-digit number from another and need to borrow from the next higher place value.

When the digit on top of a column is smaller than the digit below it, we regroup by borrowing from the next higher place value, such as the tens or hundreds place, to complete the subtraction.

Example: Let’s subtract 512 − 278

   5 1 2
– 2 7 8

 ______

Step 1:

Subtract the Ones Place

Ones column: 2 − 8 → 2 is smaller than 8, so we need to borrow.

Borrow 1 ten from the tens place: 1 ten = 10 ones.

Update digits: Tens place becomes 0, Ones place becomes 12.

Subtract: 12 − 8 = 4

Step 2:

Tens column: 0 − 7 → 0 is smaller than 7, so borrow 1 hundred from the hundreds place.

Update digits: Hundreds place becomes 4, Tens place becomes 10.

Subtract: 10 − 7 = 3

Step 3: 

Hundreds column: 4 − 2 = 2

Final answer:

   5 1 2
– 2 7 8

_________

   2 3 4

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 only for learning, it’s a skill which used in daily life. Whether figuring out how much money is left after shopping, calculating distances, or keeping track of items at home, subtracting larger numbers helps children solve real-world problems. 

• Shopping and Money: When buying items, we use subtraction to find out the remaining change. For example, if we have $500 and spend $275 on toys, the remaining amount is $500 − $275 = $225.

• Time and Schedules: Subtraction helps calculate how much time has passed or is left. For instance, if a class starts at 9:00 AM and ends at 11:45 AM, the duration is 11:45 − 9:00 = 2 hours 45 minutes.

• Travel and Distance: To know how far we still need to travel, we subtract the distance already covered from the total distance. For example, for a 350-mile trip with 120 miles completed, the remaining distance is 350 − 120 = 230 miles.

• Counting and Inventory: In a library with 300 books, if 145 are borrowed, the remaining books are 300 − 145 = 155.

• Classroom Activities: Teachers use subtraction to determine attendance. If a school has 460 students and 38 are absent, then 460 − 38 = 422 students are present.