How to Add Two-Digit Numbers with Carrying for a 9-Year-Old

Goal

Learn to add two-digit numbers by lining up tens and ones, and use carrying when the ones add up to 10 or more.

What does place value mean?

Each number has tens and ones. In 23, the 2 is tens (20) and the 3 is ones (3).

Steps to add two-digit numbers

1. Line up the numbers by their right edges so the ones line up with ones and tens with tens.
2. Add the ones digits. If the sum is less than 10, write the sum in the ones place. If the sum is 10 or more, write the ones digit of the sum and carry 1 to the tens place.
3. Add the tens digits, and add any carried 1 from the previous step. The result in the tens place (and possibly hundreds if needed) is the answer.

Examples

Example 1: 23 + 15

1. Ones: 3 + 5 = 8 → write 8 in the ones place.
2. Tens: 2 + 1 = 3 → write 3 in the tens place.
3. Answer: 38

Example 2: 37 + 28

1. Ones: 7 + 8 = 15 → write 5, carry 1.
2. Tens: 3 + 2 + 1 = 6 → write 6 in the tens place.
3. Answer: 65

Example 3: 59 + 67

1. Ones: 9 + 7 = 16 → write 6, carry 1.
2. Tens: 5 + 6 + 1 = 12. Since 12 tens = 120, write 2 in the tens place and carry 1 to the hundreds place.
3. Hundreds: carry 1 → write 1 in the hundreds place.
4. Answer: 126

Tips to practice

• Use a number line or draw tens blocks to see the carries.
• Check by estimating: 30s plus 20s is around 50s.
• Practice with different pairs of two-digit numbers to become fluent.

Practice problems

1. 14 + 23
2. 27 + 18
3. 46 + 55
4. 59 + 28
5. 83 + 19

Answers

1. 37
2. 45
3. 101
4. 87
5. 102