The school wants to buy a batch of desks and chairs. You can buy 30 desks and 60 chairs. How many sets can you buy if you buy a set?
学校想买一批课桌椅，全买桌子可以买30张，全买椅子可以买60把，如果成套的买可以买多少套？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

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

<gadget id="calculator">(1/30) + (1/60)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>