A distance is divided into three sections: uphill, flat road, and downhill. The ratio of the length of each section is 1:2:3. The ratio of the time it takes for a person to walk these three sections is 4:5:6. It is known that he travels 2.5 kilometers per hour when going uphill, and the total length of the journey is 20 kilometers. How long does it take this person to complete the journey?
一段路程分为上坡、平路、下坡三段，各段路程的长度之比是1：2：3，某人走这三段路所用的时间之比是4：5：6．已知他上坡时每小时行2.5千米，路程全长为20千米．此人走完全程需多长时间？
<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(4/3) * (5/4)</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">1 + 2 + 3</gadget>
<output>6</output>

<gadget id="calculator">6 / 4</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(4/3) * (3/2)</gadget>
<output>2</output>

<gadget id="calculator">(4/3) + (5/3) + 2</gadget>
<output>5</output>

<result>5</result>