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P. 3

Min       Sec
                                                         39      75

                                                         40      15
                                                    -    19      20

                                                         20      55


               Step 1: 15 sec < 20 sec

                           So borrow 1 minute from 40 minutes and change it into seconds.


                           60 seconds + 15 seconds = 75 seconds


                           Subtract seconds.

                           75 sec – 20 sec = 55 sec


               Step 2: Subtract minutes.

                           39 min – 19 min = 20 min


               Therefore, required answer is 20 minutes 55 seconds.




               Example 4: Find the difference between 3 hours 20 minutes and 5 hours 50
               minutes.


               Answer:


                                                     Hour      Min

                                                          5      50
                                                       -
                                                          3      20
                                                          2      30





               Step 1: 50 min > 20 min


                           Subtract minutes.

                           50 minutes – 20 minutes = 30 minutes


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