Lin Ling ran a circle on a 450-meter-long circular track. It is known that he ran 5 meters per second for the first half of the time, and 4 meters per second for the second half of the time. How many seconds did she run for the second half of the distance?
林玲在450米长的环形跑道上跑一圈，已知他前一半时间每秒跑5米，后一半时间每秒跑4米，那么她的后一半路程跑了多少秒？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">450 / (9/2) / 2</gadget>
<output>50</output>

<gadget id="calculator">50 * 5</gadget>
<output>250</output>

<gadget id="calculator">450 / 2</gadget>
<output>225</output>

<gadget id="calculator">250 - 225</gadget>
<output>25</output>

<gadget id="calculator">25 / 5</gadget>
<output>5</output>

<gadget id="calculator">225 - 25</gadget>
<output>200</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<gadget id="calculator">5 + 50</gadget>
<output>55</output>

<result>55</result>