The school bought 5 bookshelves, each with 6 layers, and each layer can hold 30 books. How many books can these bookshelves hold in total?
学校买来5个书架，每个书架有6层，每层可放30本书，这些书架一共可以放多少本书？
<gadget id="calculator">6 * 5 * 30</gadget>
<output>900</output>

<result>900</result>