jmc

Question

Trey and his mom stopped at a railroad crossing to let a train pass. As the train began to pass, Trey counted 6 cars in the first 10 seconds. It took the train 2 minutes and 45 seconds to clear the crossing at a constant speed. Which of the following was the most likely number of cars in the train?

Accepted Answer

Clearly, for every 5 seconds, 3 cars pass. It's more convenient to have everything in seconds: 2 minutes and 45 seconds=260 + 45 = 165 seconds. We then set up a ratio: 35=x165 3(165)=5x x=3(33)=99100.