Question 118784
the distances traveled by the boats are proportional to their speeds
___ since the speeds are constant, the ratio of the distances is constant


let w="width of river" ___ river is >700 yd wide
let x and y be the boat distances


at first meeting ___ x=700, y=w-700
at second meeting ___ x=w+300, y=2w-300


ratio of distances is constant, so 700/(w-700)=(w+300)/(2w-300) ___ 1400w-210000=w^2-400w-210000


1400w=w^2-400w ___ 1800w=w^2 ___ 1800=w


my first attempt at a solution had the x and y values at the first meeting reversed
___ this resulted in a width <700