A Word Problem about Boats

For younger students word problems involving moving objects are often hard to visualize. Here is the problem: "Two motorboats on opposite shores of a river start moving toward each other, but at different speeds. When they pass each other the first time, they are 700 yards from one shoreline. They continue to the opposite shore, then instantly turn around and start moving toward each other again. When they pass the second time, they are 300 yards from the other shoreline. (Their speeds, although different, remain constant.) How wide is the river?"