Rohan can travel from Delhi to Kanyakumari in 30 h. If he reduces his speed by $$\frac{1}{15}th$$, he goes 10 km less at the same time. Find the speed.

Correct option is B

Given:
Time = 30h
Formula Used:

Distance = Speed $$\times$$​ Time 
Solution:​
Let the distance between Delhi to Kanyakumari be a km.
Speed =$$\frac a{30}$$ kmph
New speed = $$\frac a{30} × (1 - \frac1{15})$$​ = $$\frac {14a}{ 450}$$​kmph
New distance = a - 10
Then,
​$$\frac {14a}{ 450} = \frac{(a - 10)} {30}$$​​
=> 14a = 15a - 150
=> a = 150 km
∴ His original speed = 150 / 30 = 5 kmph