To fold a batch of paper cranes, it takes Xiao Ming half an hour to fold them alone, and Xiao Xi takes 45 minutes to fold them alone, how many minutes will it take Xiao Ming and Xiao Xi to fold this batch of paper cranes together?
折叠一批纸鹤，小明单独折叠需要半个小时，小西单独折叠需要45分钟，则小明呵小西共同折叠这批纸鹤，需要多少分钟．
<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>