A book is 18 mm thick, and 5 books are stacked together, how thick is it?
一本书厚18毫米，5本书重叠在一起，厚多少厘米？
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">18 * (1/2)</gadget>
<output>9</output>

<result>9</result>