Teacher Wang watered the rose and Clivia at the same time today. If the rose was watered every 3 days, the Clivia was watered every 5 days. At least how many days later, water these two kinds of flowers at the same time?
王老师今天同时给月季和君子兰浇水，如果月季每3天浇一次水，君子兰每5天浇一次水．至少多少天以后给这两种花同时浇水？
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>