There are 640 story books in the library, and there are fewer science books (3/8) than story books. How many science books are there?
图书馆有故事书640本，科技书比故事书少(3/8)，科技书有多少本？
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (3/8)</gadget>
<output>5/8 = around 0.625</output>

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

<result>400</result>