Ratio of upstream speed to that of downstream speed is 3 : 5. If speed of boat…
2025
Ratio of upstream speed to that of downstream speed is 3 : 5. If speed of boat in still water is 24 km/hr then in how much time boat will cover 36 km upstream and 60 km downstream together?
- A.
4 hours
- B.
3 hours
- C.
3 hours
- D.
None of these
Attempted by 5 students.
Show answer & explanation
Correct answer: A
To find the total time taken to cover the distances upstream and downstream, we follow a logical breakdown of speed and time relationships.
Step-by-Step Analysis
Define Variables:
Let the upstream speed be 3x and the downstream speed be 5x.
The boat speed in still water is the average of the upstream and downstream speeds: (3x + 5x) / 2 = 4x.
Calculate Speeds:
We are given that the boat speed in still water is 24 km/hr.
Setting 4x = 24 km/hr, we find x = 6.
Upstream speed = 3 * 6 = 18 km/hr.
Downstream speed = 5 * 6 = 30 km/hr.
Calculate Time Taken:
Time to cover 36 km upstream = Distance / Upstream Speed = 36 / 18 = 2 hours.
Time to cover 60 km downstream = Distance / Downstream Speed = 60 / 30 = 2 hours.
Total time = 2 hours + 2 hours = 4 hours.
Correct Option
Option A: 4 hours