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    Addition oF 3-digit numBErS

                Addition without regrouping
                Example 1. Add 271 + 325.

                Solution. Write the numbers in columns and add them.
                Step 1. Add the ones.                Step 2. Add the tens.               Step 3. Add the hundreds.

                              H   T O                             H    T O                            H    T O

                              2   7    1                          2    7   1                           2   7    1
                         +    3   2    5                      +   3    2   5                      +   3    2   5

                                       6                               9   6                          5    9   6

                Therefore, 271 + 325 = 596.
                Addition with regrouping

                regrouping ones
                When we have more than 9 ones, we can regroup 10 ones into 1 ten.

                      1 ten 12 ones             2 tens 2 ones      2 tens 16 ones               3 tens 6 ones

                Example 2. Add 324 and 256.                                    H   T O
                Solution. Write the numbers in columns and                          1
                add them.                                                      3   2    4

                Step 1. Add the ones.                                     +    2   5    6

                          4 + 6 = 10 ones
                Regroup 10 ones as 1 ten 0 ones.                                       0

                Write 0 in the ones place and carry over 1 to the tens column.
                Step 2. Add the tens.                                   Step 3. Add the hundreds.

                                H    T O                                               H    T O

                                     1                                                      1
                                3    2   4                                             3    2   4

                            +   2    5   6                                         +   2    5   6

                                     8   0                                             5    8   0

                1 + 2 + 5 = 8 tens                                      3 + 2 = 5 hundreds
                Write 8 in the tens place.                              Write 5 in the hundreds place.
                Therefore, 324 + 256 = 580.

                       40        Mathematics 3

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