One day, Uncle Li drove to work at a speed of 90 km/h, but there was a traffic jam on the way to get off work, resulting in an average speed of only 45 km/h on the way to get off work. What is the average speed of Uncle Li on the way to and from work? hour.
某天李叔叔以90千米/时的速度开车上班，但下班路上出现了交通阻塞，造成下班路上平均速度只有45千米/时，则李叔叔上、下班全程的平均速度是多少千米/时．
<gadget id="calculator">90 * 2</gadget>
<output>180</output>

<gadget id="calculator">90 / 90</gadget>
<output>1</output>

<gadget id="calculator">90 / 45</gadget>
<output>2</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">180 / 3</gadget>
<output>60</output>

<result>60</result>