A man driving at \(\frac{3}{4}\)th of his original speed reaches his destination 20 minutes later than the usual time . The usual time is :

60 min

Reduces his speed to \(\frac{3}{4}\) times

Ratio             Initial   :     New 

 Speed             4     :      3

 Time               3     :      4

According to question ,  1R = 20 min

3R = 60 min