Question

Aravind and Biswanath start at the same time from their hostel and go to the ground with speeds of 30 km/h and 60 km/h, respectively. If Aravind takes 20 minutes longer than Biswanath to reach the ground, then find the distance between their hostel and the ground.
1. 28 km
2. 34 km
3. 40 km
4. 20 km

Answer 1

Correct Answer - Option 4 : 20 km

The speed of Aravind = 30 kmph
The speed of Biswanath = 60 kmph
Let the time take by Biswanath = X hours
Implies, the time taken by Aravind = X hours + 20 minutes = (X + 1/3) hours
Now,
Speed × Time = Distance
30 × (X + 1/3) = 60 × X 
⇒ 30X + 10 = 60X
⇒ 30X = 10
⇒ X = 1/3 hours = 20 minutes
Distance = 1/3 × 60 = 20 km

Hence, the distance between the hostel and the ground is 20 km.