From A to B, 40% of them are uphill, 35% are downhill, and the rest are flat. Xiao Wang goes back and forth between A and B once, a total of 3 kilometers uphill. How many kilometers are there between A and B?
从甲地到乙地，其中40%是上坡路，35%是下坡路，其余是平路，小王在甲乙两地往返一次，共走上坡路三千米．甲、乙两地相距多少千米？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(2/5) + (7/20)</gadget>
<output>3/4 = around 0.75</output>

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

<result>4</result>