The school is going to distribute exercise books to 25 classes, each class has 144 copies, and 60 copies need to be kept as spares. How many exercise books should schools buy?
学校准备发练习本，发给25个班，每班144本，还需要留60本作为备用．学校应买多少练习本？
<gadget id="calculator">144 * 25</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 + 60</gadget>
<output>3_660</output>

<result>3_660</result>