Make a cuboid iron frame with a width of 42cm, which is exactly long (6/7) and high (3/5). How long should the iron wire be at least to make such an iron frame?
做一个长方体的铁架，宽42cm，正好是长的(6/7)，同时又是高的(3/5)，做这样的铁架，至少要用多长的铁丝？
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">42 / (6/7)</gadget>
<output>49</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">42 / (3/5)</gadget>
<output>70</output>

<gadget id="calculator">49 + 42 + 70</gadget>
<output>161</output>

<gadget id="calculator">161 * 4</gadget>
<output>644</output>

<result>644</result>