A batch of books sold 80 on the first day and 120 on the second day, exactly (1/3) of the total. How many books are there in this batch?
一批书，第一天卖出80本，第二天卖出120本，恰好卖出总数的(1/3)，这批书有多少本？
<gadget id="calculator">120 + 80</gadget>
<output>200</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">200 / (1/3)</gadget>
<output>600</output>

<result>600</result>