## PROBLEM 4. FERRIES

Two ferries shuttle across a river at constant speeds, turning at the banks without losing time. They depart simultaneously from opposite banks and meet for the first time 700 feet from one of the banks, continue to the banks, return, and meet for the second time 400 feet from the opposite bank. As an oral exercise, determine the width of the river. (In the UK and US, a foot is denoted by a prime: 700 feet $-700^{\prime}$.)

![](https://cdn.mathpix.com/cropped/2024_05_21_2f4fa61a46fbb276c744g-12.jpg?height=320&width=1132&top_left_y=1510&top_left_x=470)

Fig. 5