



 
Hi Stefano, The rear of the train is moving towards the car at 50 mph and your car is moving towards the rear of the train at 85 mph. Thus the distance between the rear of the train and the car is decreasing at the rate of 50 + 85 = 135 mph. Since there are 3600 seconds in an hour that's $\large \frac{135}{3600}$ miles per second. The distance between the rear of the train and the car shrinks to 0 miles in 35 seconds. Use the fact that rate is distance over time to calculate the length of the train in miles. You probably want to convert that to feet. Penny
 


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 