A policeman went to a crime scene at a speed of 65 meters per minute to solve the case. When he set off, he took a police dog with him. The police dog ran back and forth between the two places at a speed of 100 meters per minute. Also arrived at the same time, how many kilometers did the police dogs run?
一个警察以每分钟65米的速度到一案发地破案，出发时带着一只警犬，警犬在两地间以每分100米的速度来回奔跑，当到达3900米的案发地时，警犬也同时到达，警犬跑的路程是多少千米？
<gadget id="calculator">3_900 / 65</gadget>
<output>60</output>

<gadget id="calculator">60 * 100</gadget>
<output>6_000</output>

<result>6_000</result>