There are 640 popular science books in the Tiantian Bookstore of the school, which is 60% more than the number of story books. How many story books does Tiantian Bookstore have?
学校天天书屋有科普读物640本，比故事书的本数多60%．天天书屋有故事书多少本？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 + (3/5)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">640 / (8/5)</gadget>
<output>400</output>

<result>400</result>