The library of Ge Yunfei Primary School bought 840 new story books, which is 60% of the original story books. How many original story books are there in the book?
葛云飞小学图书室新买来故事书840本，是原有故事书的60%．图书事原有故事书多少本？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">840 / (3/5)</gadget>
<output>1_400</output>

<result>1_400</result>