1 Answers
Option 2 : 9.04 hours
For car A:
Distance between 2 cities = 900 Km
25% of the distance = 900 × 1/4 = 225 Km
Speed = 75 Km/hr
∴ Time = 225/75 = 3 hrs
50% of the distance = 900 × 1/2 = 450 Km
Speed = 45 Km/hr
Time = 450/45 = 10 hours
Remaining distance = 900 – (225 + 450) = 225 Km
Speed = 50 Km/hr
Time = 225/50 = 4.5 hours
Total time taken = 3 + 10 + 4.5 = 17.5 hrs
For car B:
Since B covered its journey in 3 equal phases of time.
Average Speed = (30 + 60 + 90)/3 = 60 Km/h
⇒ B travels at an average speed of 60 Km/h.
Distance between 2 cities = 900 Km
Total time = 900/60 = 15 hrs
∴ B travels in 1st 5 hours = 30 × 5 = 150 Km
B travels in 2nd 5 hours = 60 × 5 = 300 Km
B travels in 3rd 5 hours = 90 × 5 = 450 Km
After 5 hours A will be at a distance = (225 + 90) Km = 325 Km
After 5 hours B will be at a distance = 150 Km
Distance between them = 900 – (325 + 150) = 425 Km
Now, Speed of Car A = 45 Km/hr
Speed of B = 60 Km/hr
They travel in opposite direction.
∴ Relative Speed = 45 + 60 = 105 Km/h
Time = 425/105 = 4.04 hrs
Total time = (5 + 4.04) hrs = 9.04 hrs