A batch of goods is transported by car A alone in 4 hours, and car B by itself in 5 hours. How many hours can the two cars transport the goods at the same time (3/4).
运一批货物，甲车单独运4小时完成，乙车单独运5小时完成，两车同时运多少小时可以运完这批货物的(3/4)．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</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>9/20 = around 0.45</output>

<gadget id="calculator">(3/4) / (9/20)</gadget>
<output>5/3 = around 1.666667</output>

<result>5/3 = around 1.666667</result>