The car drives straight towards the silent valley at a speed of 72 kilometers per hour. The driver presses the horn and hears an echo after 4 seconds. The speed of the sound is known to be 340 meters per second. When the echo is heard, the distance between the car and the valley is How much rice?
汽车以每小时72千米的速度笔直的开向寂静的山谷，驾驶员按一声喇叭，4秒后听到回响，已知声音的速度是每秒340米，听到回响时汽车离山谷距离是多少米？
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">340 * 4</gadget>
<output>1_360</output>

<gadget id="calculator">80 + 1_360</gadget>
<output>1_440</output>

<gadget id="calculator">1_440 / 2</gadget>
<output>720</output>

<gadget id="calculator">720 - 80</gadget>
<output>640</output>

<result>640</result>