A racing team is training. During the training, all the team members are moving forward at a speed of 35 km/h. Suddenly, team member No. 1 is moving forward at a speed of 45 km/h. Ride back at the speed of / hour until you meet up with other team members. How long has it been since the team member left the team and rejoined the team member?
某赛车队进行训练，训练时所有的队员均以35千米/时的速度前进，突然，一号队员以45千米/时的速度前进，行进20千米后调转车头，仍以45千米/时的速度往回骑，直到与其他队员会合．此队员从离队开始，到与队员重新会合，经过了多长时间？
<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<gadget id="calculator">45 + 35</gadget>
<output>80</output>

<gadget id="calculator">40 / 80</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>