Xiao Ming's home is 14 kilometers away from the bookstore. On Sunday, Xiao Ming's father drove from home to the bookstore to buy books. If a car needs (5/7) liters of oil for every 10 kilometers it travels, how many liters of oil are needed for a round trip?
小明家距书城14千米．周日，小明爸爸从家里出发开车去书城购书．若汽车每行驶10千米需用油(5/7)升，那么，来回一趟需用油多少升？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) / 10</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(1/14) * 14 * 2</gadget>
<output>2</output>

<result>2</result>