The school originally planned to send 15 students to participate in the mathematics summer camp, but actually sent 21 students. What percentage was more than planned?
学校原计划派出15名同学参加数学夏令营活动，实际派出了21名同学，实际比计划多派出了百分之几？
<gadget id="calculator">21 - 15</gadget>
<output>6</output>

<gadget id="calculator">6 / 15</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>