The school distributes (1/3) of the purchased books to the fifth and sixth grades at a ratio of 4:5. It is known that there are 80 books for the fifth grade, how many books did the school buy in total?
学校把购进图书的(1/3)按4：5分给五、六两个年级．已知五年级分得80本，学校共购进图书多少本？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

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

<gadget id="calculator">80 / (4/9) / (1/3)</gadget>
<output>540</output>

<result>540</result>