Two trains traveling on parallel tracks are going toward eac

Two trains traveling on parallel tracks are going toward each other from a distance of 960 kilometers. if one train moving at 100 kilometers per hour and the other is moving at 140 kilometers per hour, after how many hours will the trains pass each other?

Solution

Their approach rate is 100+140 or 240 km/h and 960/240 = 4 hours. But here is the way to do it with algebra. Make this chart: RATE TIME DISTANCE Slower train Faster train Put in the rates and t for the time until they pass: RATE TIME DISTANCE Slower train 100 t Faster train 140 t Then use DISTANCE = RATE x TIME to fill in the distances RATE TIME DISTANCE Slower train 100 t 100t Faster train 140 t 140t The the sum of their distances traveled must equal the 960 km they were at the start, so the equation is Slower train\'s distance traveled to point of passing + Faster train\'s distance to point of passing = 960 km. 100t + 140t = 960 Solve that and get 4 hours.