Two boats head directly toward each other, one of them traveling 12 miles per hour and the other traveling 17 miles per hour. They begin at a distance of 20 miles from each other. How far apart are they one minute before they collide?
Think of the distance between the boats. This distance is decreasing at a rate of 12 + 17 = 29 miles per hour. One minute is one-sixtieth of an hour so in one minute the distance between them changes by 29 times 1/60 = 0.4833 miles. Thus one minute before they collide they will be 0.4833 miles apart.Cheers,