It took Xiao Ming a mountain tour on Sunday. It took 45 minutes to climb from the foot of the mountain to the top of the mountain, and only 30 minutes to return along the original road. How much faster is the speed of going down the mountain than going up the mountain.
星期天小明爬山游览，从山脚下爬到山顶用了45分，沿原路返回时只用了30分，下山速度比上山快多少．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 45</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/30) - (1/45)</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">(1/90) / (1/45)</gadget>
<output>1/2 = around 0.5</output>

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