A boat whose velocity through the water is 20 km/h is moving in a river whose current is 6 km/in relative to the riverbed. The velocity of the boat relative to the riverbed must be between
A) 6 and 20 km/h.
B) 6 and 26 km/h.
C) 12 and 20 km/h.
D) 12 and 26 km/h.

Question

Quizplus · Accepted Answer

The velocity of the boat relative to the riverbed can be calculated by adding or subtracting the velocity of the river's current from the boat's velocity through the water. When moving downstream, the boat's velocity relative to the riverbed is the sum of its own velocity and the current's velocity (20 km/h + 6 km/h = 26 km/h). When moving upstream, the boat's velocity relative to the riverbed is its velocity minus the current's velocity (20 km/h - 6 km/h = 14 km/h). Therefore, the boat's velocity relative to the riverbed must be between 14 and 26 km/h.

A Boat Whose Velocity Through the Water Is 20 Km/h