If a student walks at a speed 30% more than the usual speed, he reaches 15 min earlier to his destination. How much time (in minutes) does he take to reach his destination normally?

65

Let initial speed = 100

New speed = 100 + 30 % of 100 = 130

As per the question,

The ratio of

 speed                10 : 13

Time                    13 : 10

( Time is inversely proportional ti Speed )

Difference 3R = 15 minutes

1R = \(\frac{15}{3}\) = 5 minutes

Usual Time taken  = 13R = 13 × 5   = 65 minutes