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    AddItIon And SubtrACtIon togEtHEr

                Example 1. Solve: 4578 – 3795 + 2563 – 1789

                Solution.
                Method 1. We start the operations from the left and move to the right stepwise.

                Step 1:       4 5 7 8                  Step 2:           7 8 3               Step 3:       3 3 4 6

                           – 3 7 9 5                              + 2 5 6 3                            – 1 7 8 9
                                  7 8 3                              3 3 4 6                               1 5 5 7

                Method 2. First, we add the numbers with + signs and – signs separately. Then, we
                find the difference of the two sums as follows:

                Step 1:       4 5 7 8                  Step 2:       3 7 9 5                 Step 3:       7 1 4 1
                           + 2 5 6 3                              + 1 7 8 9                            – 5 5 8 4

                              7 1 4 1       (+ sign)                 5 5 8 4       (– sign)                1 5 5 7

                So, 4578 – 3795 + 2563 – 1789 = 1557.

                Example 2. In a small town, there are 2135 men and 1987 women. If the population of
                the town is 8000, how many children are there in the town?

                Solution. Number of children in the town                       8 0 0 0                     5 8 6 5
                               = 8000 – 2135 – 1987                         – 2 1 3 5                  – 1 9 8 7

                               = 3878                                          5 8 6 5                     3 8 7 8
                Thus, the number of children in the town is 3878.

                            Exercise 3G

                    1.  Solve:

                        a.   3231 –  1965 + 987                           b.   3256 – 4589 + 1634
                        c.   2634 + 1687 – 834 – 1622                     d.   8532 – 1986 + 3756 – 5288

                        e.   4702 + 8329 – 9561 – 3385                    f.   7008 – 9522 + 9987 – 832
                    2.  Subtract the sum of 2370 and 4599 from 8220.

                    3.  Subtract the difference of 4980 and 3895 from 6910.
                    4.  Subtract 6998 from the sum of 5334 and 4653.

                  5.  7034  persons  visited  the  zoo  on  the  last  three  days  of  a
                        week. If 3548 and 1698 persons visited the zoo on Friday and
                        Saturday respectively, how many persons visited the zoo on
                        Sunday?

                       66        Mathematics 3

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