Addition up to 99
Adding two-digit numbers is simpler. Here’s an example:
Let’s add 23 and 45.
1. Write the numbers one below the other, aligning the digits by place value:
23
+ 45
_____
2. Add the digits in the units place (rightmost digits):
– The digits are 3 and 5.
– 3 + 5 = 8.
– Write down 8 in the units place.
23
+ 45
______
8
3. Add the digits in the tens place:
– The digits are 2 and 4.
– 2 + 4 = 6.
– Write down 6 in the tens place.
“`
23
+ 45
____
68
So, 23 + 45 = 68.
Here’s the breakdown:
– Units place: 3 + 5 = 8. Write down 8.
– Tens place: 2 + 4 = 6. Write down 6.
Therefore, the sum of 23 and 45 is 68.
Regrouping
Regrouping (also known as carrying) is a method used in addition when the sum of the digits in one place value column exceeds 9. Here’s a simple way to explain this to a first-grade student, using an example:
Example: Adding 27 and 38
1. Write the numbers one below the other, aligning the digits by place value:
27
+38
_________
2. Add the digits in the units place (rightmost digits):
– The digits are 7 and 8.
– 7 + 8 = 15.
– Write down the 5 in the units place and carry over the 1 to the tens place.
27
+ 38 ___________
5 (carry 1)
3. Add the digits in the tens place along with the carryover:
– The digits are 2 and 3, with a carryover of 1.
– 2 + 3 + 1 = 6.
– Write down 6 in the tens place.
`
27
38
_______
65
So, 27 + 38 = 65.
Simple Explanation :
1. Line up the numbers:
– Write them so the tens and units digits are in columns.
2. Add the units digits:
– First, add the numbers in the units place.
– If the sum is 10 or more, remember to carry over.
3. Carry over:
– If the sum of the units place is more than 9, keep the units digit and carry over the tens digit to the next column.
4. Add the tens digits:
– Add the tens digits along with any number you’ve carried over.