Two round wheels, big and small, have a difference of (2/5) meters in circumference. They roll for a certain distance. The big circle needs to roll 4 times, and the small circle needs to roll 5 times. How many meters is this distance?
大小两个圆轮，它们的圆周长相差(2/5)米，同滚一段距离，大圆要滚动4周，小圆要滚动5周，这段距离是多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(2/5) / (1/20)</gadget>
<output>8</output>

<result>8</result>