A ferry's speed relative to the water is 5 km/h and the current is 3 km/h; the river is 600 m wide. How much longer does the shortest-path crossing (landing exactly opposite) take than the quickest crossing (heading straight across)?

Question

Accepted Answer

1 min 48 s. Quickest: all 5 km/h across ⇒ 0.6/5 h = 7 min 12 s. Shortest path: across component = √(25 − 9) = 4 km/h ⇒ 0.6/4 h = 9 min. Difference = 1 min 48 s.

A ferry's speed relative to the water is 5 km/h and the current is 3 km/h; the river is 600 m wide. How much longer does the shortest-path crossing (landing exactly opposite) take than the quickest crossing (heading straight across)?

Step-by-Step Solution

Master this topic in 30 minutes a day.

More Boats & Streams practice