There is a batch of goods at the station. Car A can transport half of the goods in 4 hours alone, and car B can transport 1/5 of the goods in 2 hours alone. Now how many hours will it take for A and B to transport the goods together?
车站有一批货物，甲车单独4小时可以运这批货物的一半，乙车单独2小时可以运这批货物的(1/5)，现在甲、乙合运要多少小时运完．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) / 4</gadget>
<output>1/8 = around 0.125</output>

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

<gadget id="calculator">(1/5) / 2</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/8) + (1/10)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">1 / (9/40)</gadget>
<output>40/9 = around 4.444444</output>

<result>40/9 = around 4.444444</result>