Rocio leaves point A traveling due east at 40 miles per hour. At the same moment, Li leaves point A traveling due west at 50 miles per hour. After how many hours will they be 405 miles apart?)
Their speed of separation will be equal to the sum of their speeds because they are in opposite directions. Speed of separation = 40 + 50 = 90 miles per hour
Time = distance / speed Time = 405 / 90 Time = 4.5 hours
