Two passenger trains, A and B, leave at the same time from two places 180 kilometers away. A travels 50 kilometers per hour, and B travels 40 kilometers per hour. A dog runs back and forth between the two at a speed of 80 kilometers. , How many kilometers did the dog travel until the two met?
甲、乙两列客车同时从180千米的两地相对开出，甲每小时行50千米，乙每小时行40千米，一只狗以80千米的速度在两人之间来回奔跑，直到两人相遇狗行了多少千米？
<gadget id="calculator">50 + 40</gadget>
<output>90</output>

<gadget id="calculator">180 / 90</gadget>
<output>2</output>

<gadget id="calculator">2 * 80</gadget>
<output>160</output>

<result>160</result>