<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 A car drives straight towards a quiet valley at a speed of 72 kilometers per hour. The driver honks the horn, and 4 seconds later, hears an echo. Given that the speed of sound is 340 meters per second, find the distance in meters between the car and the valley when the echo is heard. Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
640
A car drives straight towards a quiet valley at a speed of 72 kilometers per hour. The driver honks the horn, and 4 seconds later, hears an echo. Given that the speed of sound is 340 meters per second, find the distance in meters between the car and the valley when the echo is heard.
test