A batch of wood can make 90 pieces if only chairs are made, and 60 pieces can be made if only tables are made. Now, if such tables and chairs are made, how many sets can be made in total?
一批木材，如果只做椅子可以做90张，如果只做桌子可以做60张，现在如果做成这样的桌椅，共可做多少套？
<gadget id="calculator">1 / 90</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/90) + (1/60)</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">1 / (1/36)</gadget>
<output>36</output>

<result>36</result>