A child, who is 45 m from the bank of a river, is being carried helplessly downstream by the river's swift current of 1.0 m / s. As the child passes a lifeguard on the river's bank, the lifeguard starts swimming in a straight line (Fig. 3-46) until she reaches the child at a point downstream.

If the lifeguard can swim at a speed of 2.0 m / s relative to the water, how long does it take her to reach the child? How far downstream does the lifeguard intercept the child?

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|1.0 m/s 2.0 m/s 45 m