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    regrouping tens and ones

                Example 4. Add 254 and 168.
                Solution. Write the numbers in columns and add them.

                Step 1. Add the ones and regroup.                       Step 2. Add the tens and regroup.

                                         H   T O                                               H   T O

                                              1                                                1    1
                                         2   5    4                                            2   5    4

                                    +    1   6    8                                       +    1   6    8

                                                  2                                                2    2

                4 + 8 = 12 ones = 1 ten 2 ones                          1 + 5 + 6 = 12 tens = 1 hundred 2 tens

                Write 2 in the ones place and carry                     Write 2 in the tens place and carry
                over 1 to the tens column.                              over 1 to the hundreds column.

                Step 3. Add the hundreds.
                                                                              H   T O
                                     1 + 2 + 1 = 4 hundreds
                                                                              1    1
                Write 4 in the hundreds place.
                Therefore, 254 + 168 = 422.                                   2   5    4
                                                                         +    1   6    8

                                                                              4   2    2

                regrouping Hundreds

                When we have more than 9 hundreds, we can regroup 10 hundreds into 1 thousand.

                             a.  10 hundreds = 1 thousand

                             b.  12 hundreds = 1 thousand 2 hundreds

                Example 5. Add 765 and 389.

                Solution. Write the numbers in columns and add them.
                                                                                                       Th H      T O
                Step 1. Add the ones and regroup.
                                                                                                                 1
                                       5 + 9 = 14 ones
                                                                                                            7   6    5
                                               = 1 ten 4 ones
                                                                                                   +        3   8    9
                Write 4 in the ones place and carry over 1 to the tens column.
                                                                                                                     4

                       42        Mathematics 3

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