The students participated in the standard-reaching activities. There were originally 50 students who achieved excellent grades, but now there are 15 more students. What percentage increase?
同学们参加达标活动，达到优的原有50人，现在增加了15人，增加了百分之几？
<gadget id="calculator">15 / 50</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>