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    E:\Working\Focus_Learning\Math_Genius_3_(11-09-2024)\Open_Files\CHAP_03
                 \ 12-Sep-2024  Surender Prajapati   Proof-5                                  Reader’s Sign _______________________ Date __________

                  eStimating difference

                  Like addition, we can also estimate the difference by rounding off.
                  Example 1: Estimate the difference of 64 and 87 by rounding them to the nearest 10.

                  Then, compare it with their actual difference.

                  Solution:      Actual difference   Estimated difference
                                       t    O                     t   O

                                       8    7   rounded up        9    0
                                    – 6     4  rounded down    – 6     0
                                       2    3                     3    0

                                 The estimated difference is greater than the actual one.
                  Example 2: A shopkeeper had 662 balls. He sold 245 balls. Estimate the number of unsold

                  balls by rounding off to the nearest 10. Is the number of balls left unsold more than or
                  less than 400?
                  Solution:      Actual difference      Estimated difference

                                           H    t   O                      H    t   O
                                            6   6    2  rounded down       6    6    0
                                        – 2     4    5   rounded up     – 2     5    0
                                            4   1    7                     4    1    0

                                 The estimated number of unsold balls is 410.
                                 Clearly, the shopkeeper has more than 400 balls left unsold with him.

                           Practice time 3d

                       Find the estimated difference by rounding to the nearest 10. Also, find the actual
                       difference and compare.

                        1. Actual difference       Estimated difference  2. Actual difference       Estimated difference

                               t    O                   t   O                         t   O                   t   O
                               8    7   round off                                     9   4   round off
                            – 2     3   round off   –                             – 6     5   round off    –

                        3. Actual difference       Estimated difference   4. Actual difference      Estimated difference

                               H    t   O                   H    t   O           H    t   O                   H   t    O

                               1    6   7   round off                            2    6   4   round off
                            –       9   4   round off    –                    – 1     8   5   round off    –

                  Mathematics-3                                                                                          59

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