There is a batch of wood that can be used to make 20 desks or 30 chairs. How many sets can be made of the same set of desks and chairs?
有一批木料，可以做同样的课桌20张或同样的椅子30把，现在要做同样成套的课桌椅，可以做多少套．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<result>12</result>