What is Adding Three-Digit Numbers?

S1-SA1-0045

Grade Level:

Class 3

Maths, Computing, AI

Definition

What is it?

Adding three-digit numbers means combining two or more numbers that each have hundreds, tens, and ones places. We add them column by column, starting from the ones place, just like adding smaller numbers.

Simple Example

Quick Example

Imagine your school library has 245 storybooks and your class donates 132 more storybooks. To find the total number of storybooks, you would add 245 and 132. This is an example of adding three-digit numbers.

Worked Example

Step-by-Step

Let's add 358 and 234.

1. Write the numbers one below the other, aligning the ones, tens, and hundreds columns:
358
+ 234
-----

2. Add the ones column (8 + 4). 8 + 4 = 12. Write down 2 in the ones place and carry over 1 to the tens column.
358
+ 234
-----
2 (carry over 1 to tens)

3. Add the tens column (5 + 3 + 1 carried over). 5 + 3 + 1 = 9. Write down 9 in the tens place.
358
+ 234
-----
92

4. Add the hundreds column (3 + 2). 3 + 2 = 5. Write down 5 in the hundreds place.
358
+ 234
-----
592

So, 358 + 234 = 592.

Why It Matters

Understanding addition is fundamental for many advanced topics in Maths, Computing, and even Artificial Intelligence. Data analysts use it to sum up large datasets, while game developers might use it to calculate scores or resource totals. It's a core skill for problem-solving in many careers.

Common Mistakes

MISTAKE: Not aligning the numbers correctly by place value (ones under ones, tens under tens). | CORRECTION: Always write numbers vertically, making sure digits with the same place value are in the same column. Use graph paper if it helps.

MISTAKE: Forgetting to carry over a digit to the next column when the sum is 10 or more. | CORRECTION: When a column's sum is 10 or greater, write the ones digit of the sum in that column and carry the tens digit to the next column on the left.

MISTAKE: Adding from left to right (hundreds first) instead of right to left (ones first). | CORRECTION: Always start adding from the rightmost column (ones place) and move towards the left. This ensures any carried-over digits are included correctly.

Practice Questions

Try It Yourself

QUESTION: Add 123 + 456 | ANSWER: 579

QUESTION: What is the sum of 587 and 324? | ANSWER: 911

QUESTION: A train travelled 475 km on Monday and 368 km on Tuesday. What is the total distance it travelled in these two days? | ANSWER: 843 km

MCQ

Quick Quiz

What is 605 + 198?

703

803

793

813

The Correct Answer Is:

Adding the ones (5+8=13), we get 3 and carry over 1. Adding the tens (0+9+1=10), we get 0 and carry over 1. Adding the hundreds (6+1+1=8), we get 8. So the total is 803.

Real World Connection

In the Real World

When shopkeepers calculate the total bill for three items costing, say, Rs. 235, Rs. 148, and Rs. 300, they use addition of three-digit numbers. Even online shopping apps like Flipkart or Amazon do this automatically to show your cart total.

Key Vocabulary

Key Terms

SUM: The result of adding two or more numbers | CARRY OVER: Moving a digit to the next column when the sum of a column is 10 or more | PLACE VALUE: The value of a digit based on its position in a number (ones, tens, hundreds) | DIGIT: A single symbol used to make numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

What's Next

What to Learn Next

Now that you've mastered adding three-digit numbers, you can move on to 'Subtracting Three-Digit Numbers' or 'Adding Four-Digit Numbers'. These concepts build directly on the column method and carrying over you learned here!