It takes Xiaolin 1.5 minutes to go from the first floor to the fourth floor, and 1 minute to go from the fourth floor to the first floor. How many seconds does it take Xiaolin to go up and down one floor?
小林从一楼到四楼要用1.5分钟，从四楼到一楼要用1分钟，小林上、下一层楼要用多少秒．
<gadget id="calculator">1.5 * 60</gadget>
<output>90</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">30 + 20</gadget>
<output>50</output>

<result>50</result>