4 librarians are repairing books. On average, each person repairs 45 books per day. They have been repairing for 3 days. How many books have they repaired in total?
图书馆4位管理员修补图书，平均每人每天修补45本，已经修补了3天，共修补了多少本？
<gadget id="calculator">45 * 4 * 3</gadget>
<output>540</output>

<result>540</result>