Correct Answer - Option 3 : 13.33 km/h
Given:
Initial speed = 4km/ h
Intial time = 5 hours
Time reduced to = 1 hours 30 minutes
Formula used:
Speed = Distance/ Time
m/ s = 5/ 18 km/hr
Calculation:
Distance covered = 4 × 5
⇒ Distance covered = 20 km
⇒ Speed needed = 20/ 1.5
⇒ Speed needed = 20 × 10/ 15
⇒ Speed needed ≈ 13.33 km/ h
∴ speed needed is 13.33 km/h