If a person reduces his speed by 25% , he takes 28 min to reach his destination . Find the time taken by him to reach his destination if he increases his speed by 16.66% .

18 min

Speed is reduced by 25%  = \(\frac{1}{4}\)

Ratio             Initial   :     New 

 Speed             4     :      3

 Time               3     :      4

According to question ,  4R = 28 min 

1R = 7 min 

3R = 21 min  ( initial time ) 

Speed is increases by 16.66% = \(\frac{1}{6}\)

Ratio             initial   :     new 

Speed             6       :      7

 Time               7      :      6

We know initial time is 21 min . 7R  =  21 min 

                                              1R  = 3min 

                                              6R  = 18 min