A section of the journey is divided into three sections: uphill, flat road, and downhill. Each section was planned to be completed in 5 days, but it only took 4 days. How many percent did Wavelet actually use compared to the original plan? The ratio of each distance is 2:3:4, and the ratio of the time it takes for wavelet to complete the three distances is 4:5:6. It is known that his uphill speed is 4 kilometers per hour, and the total distance traveled is 36 kilometers. How long does it take for wavelet to complete the journey?
一段路程分上坡、平路、下坡三段，各段路程计划5天完成，结果只用了4天，小波实际所用效率比原计划提高了百分之几？各段路程比是2：3：4，小波走完这三段路程所用的时间比是4：5：6．已知他上坡速度是每时4千米，路程总长36千米．小波走完全程需要多少时？
<gadget id="calculator">2 + 3 + 4</gadget>
<output>9</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">(2/9) / 4 / 4</gadget>
<output>1/72 = around 0.013889</output>

<gadget id="calculator">4 + 5 + 6</gadget>
<output>15</output>

<gadget id="calculator">36 * (1/72) * 15</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>