Let's test your logic skills Captain! Johnny can row at 5 kmph in still water. If the velocity of the current is 1 kmph and it takes him 1 hour to row to the supply ship and come back, how far is the supply ship? 3.8km 1.5km 2.4km 3km
Answers
Answer ⇒ Option (c). 2.4 km.
Explanation ⇒
Let the distance between Johnny and supply ship be d km.
Velocity of the Johnny in still water = 5 kmph.
Velocity of the current = 1 kmph.
∴ Velocity by which Johny wil go = 5 + 1
= 6 kmph.
∴ Time taken by it (t₂) = d/6
In second case,
Velocity = 5 - 1
= 4 kmph.
∴ Time taken (t₂) = d/4
∵ t₁ + t₂ = 1
∴ d/6 + d/4 = 1
⇒ (2d + 3d)/12 = 1
⇒ 5d = 12
∴ d = 2.4 km.
∴ Distance between the Johnny and the Supply ship is 2.4 km.
Hence, Option (c). is correct.
Hope it helps.
speed of the boat in still water = 5 km/h
Speed of the stream = 1 km/h
Let the distance one way be x
Upstream:
Speed = 5 + 1 = 6km/h
Time needed = Distance ÷ Speed
Time = x ÷ 6 = x/6 hour
Downstream:
Speed = 5 - 1 = 4 km/h
Time needed = Distance ÷ Speed
Time = x ÷ 4 = x/4 hour
Solve x:
Given that the total time needed is 1 hour
x/6 + x/4 = 1
5/12 x = 1
x = 1 ÷ 5/12 = 12/5 = 2.4 km
Answer: The distance to the supply ship is 2.4 km