A sock knitting machine (1/42) can weave a pair of socks in an hour, how many pairs of socks can be woven in half an hour? What is the correct column
一台织袜机(1/42)小时织一双袜子，半小时可以织多少双袜子？列式正确的是多少
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 42</gadget>
<output>1/42 = around 0.02381</output>

<gadget id="calculator">(1/2) / (1/42)</gadget>
<output>21</output>

<result>21</result>