The school library bought 840 new storybooks, which are (3/5) of the original storybooks. How many original storybooks are there in the library?
学校图书室新买故事书840本，是原有故事书的(3/5)，图书室原有故事书多少本？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

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

<result>1_400</result>