Xiaoqiang started to practice brush calligraphy at 2:30 in the afternoon and did not finish until 5:30. If he practiced 6 characters per hour, how many characters did he practice in the whole afternoon?
小强下午2：30开始练毛笔字，到5：30才练完，如果他每小时练6篇字，整个下午他练了多少篇字？
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>