To fold a batch of paper airplanes, if A alone takes half an hour to complete folding, B alone takes 45 minutes to complete folding, if two people fold together, how many minutes will it take to complete.
要折叠一批纸飞机，若甲单独折叠要半个小时完成，乙单独折叠需要45分钟完成，若两人一起折叠，需要多少分钟完成．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 45</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/30) + (1/45)</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">1 / (1/18)</gadget>
<output>18</output>

<result>18</result>