Ship’s Speed:

Imagine the water current is like a moving sidewalk helping the ship downstream and slowing it upstream. Here’s how to find the ship’s speed and the current’s speed:

• Ship’s speed in still water: Add the downstream and upstream speeds, then divide by 2: (77 km/h + 67 km/h) / 2 = 72 km/h (average speed)
• Current’s speed (stream): Subtract the upstream speed from the downstream speed: 77 km/h – 67 km/h = 10 km/h (the difference is the current’s effect)

Ship Crossing the Dockyard:

To find how long the ship takes to cross the dockyard in still water, we can use a simple trick:

• Imagine the ship is standing still, and the dockyard is moving at the ship’s speed in still water (72 km/h).
• Since the small boat takes 80 seconds to cross at 36 km/h, the dockyard (effectively moving at 72 km/h) would take half the time: 80 seconds / 2 = 40 seconds (because the dockyard is moving twice as fast)

Lengths (Optional):

Unfortunately, with the given information, we cannot determine the exact lengths of the ship and the dockyard. We only know the speeds and times.