The printing factory binds a batch of textbooks, 36,000 volumes are bound every day, and it takes 15 days to complete. If 40,000 volumes are bound every day, how many days will it take to complete the task?
印刷厂装订一批课本，每天装订3.6万册，需要15天完成．如果每天装订4万册，多少天完成任务？
<gadget id="calculator">15 / 4</gadget>
<output>15/4 = around 3.75</output>

<gadget id="calculator">3.6 * (15/4)</gadget>
<output>13.5</output>

<result>13.5</result>