Answer
23s; 23m
Work Step by Step
The lifeguard is carried downstream at the same rate as the child. We only need to deal with the horizontal motion to find the time.
t = (45 m)(2.0 m/s) = 22.5 s. The lifeguard will reach the child in approximately 23 seconds.
The river carries both of them downstream a distance of (1.0 m/s)(22.5 s) = 22.5 m. The lifeguard will intercept the child at approximately 23 meters downstream.
