A car goes back and forth between A and B. It takes 4 hours to go, and the speed increases (1/5) when it comes back. How many hours does it take to come back?
一辆汽车往返与甲、乙两地，去时用了4小时，回来时速度提高了(1/5)，回来时用了多少小时．
<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 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(1/4) * (6/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / (3/10)</gadget>
<output>10/3 = around 3.333333</output>

<result>10/3 = around 3.333333</result>