The distance between two stations A and B is 440 meters. A large cart and a small cart drive oppositely from the two stations. The cart travels 35 kilometers per hour, the small cart travels 45 kilometers per hour, and a swallow travels at a speed of 50 kilometers per hour. Set off at the same time as the big cart, fly towards the small cart, meet the small cart, turn back and fly towards the cart, meet the large cart, fly back to the small cart, and keep flying like this, how many kilometers does the swallow fly before the two carts meet?
甲乙两站相距440米，一辆大车和一辆小车从两站相对开出，大车每小时行35千米，小车每小时行45千米，一只燕子以每小时50千米的速度和大车同时出发，向小车飞去，遇到小车又折回向大车飞去，遇到大车又往回飞向小车，这样一直飞下去，燕子飞了多少千米两车才相遇？
<gadget id="calculator">45 + 35</gadget>
<output>80</output>

<gadget id="calculator">440 / 80</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">(11/2) * 50</gadget>
<output>275</output>

<result>275</result>