It takes 90 seconds to count 100 exercise books, how many seconds will it take to count 10,000 exercise books at this speed.
数100本练习本要用90秒，照这样的速度数10000本练习本大约要用多少秒．
<gadget id="calculator">10_000 / 100</gadget>
<output>100</output>

<gadget id="calculator">90 * 100</gadget>
<output>9_000</output>

<result>9_000</result>