A girl reduced his speed to 3/5th and reaches her destination in 25 hours . If she had walked at her initial speed then how much time had she saved ?

10 hours

Ratio                            old     :      new

Speed                          5        :        3

Time                            3        :       5

According to question , 5R = 25 hours

                                  1R = 5 hours

    time saved if she walked by his usual speed is ,

                                 2R  =  10 hours