There are two stacks of the same "Happy Classroom" workbooks, the first stack has 45 books and is 67.5cm thick; the second stack is 90cm thick. About how many books are there in the second stack?
有两摞同样的《快乐课堂》练习册，第一摞有45本，厚67.5cm；第二摞厚90cm．第二摞大约有多少本？
<gadget id="calculator">67.5 / 45</gadget>
<output>1.5</output>

<gadget id="calculator">90 / 1.5</gadget>
<output>60</output>

<result>60</result>