It took 15 minutes for a person to climb a mountain. When going down the mountain along the original road, the speed increased (1/4). How many minutes did it take to go down the mountain?
一个人登山，上山用了15分钟，沿着原路下山的时候，速度加快了(1/4)，下山用了多少分钟．
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(1/15) * (5/4)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<result>12</result>