Addition of two numbers:

Adding a 2-digit number and a 1-digit number involves adding a number in the tens place and one's place (the 2-digit number) with a number that only has one place (the 1-digit number). The process starts by adding the ones digits first. If the result is more than 9, you regroup (carry over) the extra value to the tens place.

Step-by-Step Process:

1. Align the numbers by place value (ones under ones, tens under tens).
2. Add the one-place digits. If the sum is greater than 9, write down the one digit and carry over the tens digit to the next column.
3. Add the tens place. If there is a carry-over from the one's place, add it to the tens digit of the 2-digit number.

Example 1:

Without regrouping, add numbers 34 and 5.

Solution:

• Write the numbers aligned by place value: 34+5.
• Add the ones in place:
  • 4 + 5 = 9. Write 9 in one place.
• Move to the tens place:
  • There's no number to add to 3, so just bring down the 3.
• Final solution: 34 + 5 = 39.

Example 2:

With Regrouping, Add 57 and 8.

Solution:

• Write the numbers aligned by place value: 57 + 8.
• Add the ones in place:
  • 7 + 8 = 15. Write 5 in the one's place and carry over 1 to the tens place.
• Move to the tens place:
  • 5 + 1 (carry-over) = 6.
• Final solution: 57 + 8 = 65.

Example 3:

Lily has 46 apples, and her friend gives her 7 more apples. How many apples does Lily have in total?

Solution:

• Write the numbers to add: 46 + 7.
• Add the ones in place:
  • 6 + 7 = 13. Write 3 in the one's place and carry over 1 to the tens place.
• Move to the tens place:
  • 4 + 1 (carry-over) = 5.
• Final solution: 46+7=53.

Why it matters:

Mastering 2-digit addition builds essential problem-solving skills and forms the foundation for more advanced math concepts.