A hiker is 1 km upstream from a bridge on one bank of a river that is 0.5 km wide
MATHEMATICS · Single correct · A Level · Mathematics · Differentiation · Differentiation
Problem
A hiker is 1 km upstream from a bridge on one bank of a river that is 0.5 km wide. The hiker can walk along the bank at 5 km/h and row straight across the river at 3 km/h. Let x be the distance (in kilometers) the hiker walks downstream before beginning to row (0≤x≤1). Which value of x minimizes the total travel time to the bridge on the opposite bank?
(a) 0.38 km
(b) 0.63 km
(c) 1.00 km
(d) 0.25 km