🔢 Addition with Regrouping

When we add and a column makes 10 or more, we cannot write two digits in one place. So we regroup (also called carrying): keep the ones digit and carry the extra ten to the next column on the left.
Example: in 27 + 5, the ones are 7 + 5 = 12. Write 2 in the ones place and carry 1 ten to the tens column.
Always add from right to left: ones first, then tens, then hundreds.

The same regrouping idea works for 3-digit and 4-digit numbers — you may carry more than once. Stack the numbers so the place values line up, then add each column from the right.
In a word problem, look for words like altogether, in all, total, sum — they tell you to add.