Master Li completed (2/7) of a batch of parts in (1/2) hour, and he completed ((())/(())) of this batch of parts on average per hour. According to this calculation, how many hours can he complete This batch of parts.
李师傅(1/2)小时完成了一批零件的(2/7)，他平均每小时完成这批零件的((())/(()))，照这样计算，他多少小时可以完成这批零件．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(2/7) / (1/2)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 / (4/7)</gadget>
<output>7/4 = around 1.75</output>

<result>7/4 = around 1.75</result>