The school bought some new books and lent out 40, which is exactly two-fifths of the total number of new books. How many new books did the school buy?
学校买来一些新书，借出40本，这个数目正好是新书总数的五分之二．学校买来新书多少本．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 / (2/5)</gadget>
<output>100</output>

<result>100</result>