When the escalator stops running, it takes a child 90 seconds to walk the 60-meter-long escalator. When the escalator is running, it takes 60 seconds to send passengers from the bottom to the top. If a child is walking on a running escalator, ask how many seconds it takes for the child to reach the top from the bottom of the escalator.
自动扶梯停止运行时，一个小孩要用90秒钟才能走完60米长的自动扶梯．自动扶梯运行时则可用60秒钟将乘客从底端送到顶端．若小孩在运行的自动扶梯上行走，问小孩从扶梯底端到达顶端需要多少秒．
<gadget id="calculator">1 / 90</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/90) + (1/60)</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">1 / (1/36)</gadget>
<output>36</output>

<result>36</result>