The school bought exercise books and distributed them to 6 grades on average. Each grade has three classes and each class has 40 students. How many exercise books did the school buy in total?
学校买来练习本，平均分给6个年级，每个年级有三个班，每班有40个同学，学校一共买来多少本练习本？
<gadget id="calculator">6 * 3 * 40</gadget>
<output>720</output>

<result>720</result>