Correct Answer - Option 1 : 25 hours
Given:
Downstream distance = 25 km
Time taken = 5 hours
Speed of Boat : Speed of current = 3 : 2
Formula Used:
Speed = Distance/Time
D = B + S
U = B - S
where, D → Downstream speed, U → Upstream speed, B → Speed of boat in still water, S → Speed of stream.
Calculations:
Let the speed of boat and speed of stream be 3x and 2x respectively.
Speed = Distance/Time
⇒ D = 25/5
⇒ D = 5 km/hr
Now, D = B + S
⇒ 5 = 3x + 2x
⇒ 5 = 5x
⇒ x = 1
B = 3x = 3 × 1
⇒ B = 3 km/hr
Similarly,
S = 2x = 2 × 1
⇒ S = 2 km/hr
Now, U = B - S
⇒ U = 3 - 2 = 1 km/hr
Speed = Distance/Time
⇒ 1 = 25/Time
⇒ Time = 25 hours
∴ The time taken by ship to cover 25 km upstream is 25 hours.
