Zhuang Zhuang planned to practice writing 30 Chinese characters a day, and actually completed the plan in the morning (7/15) and in the afternoon (11/15). By what percentage did Zhuang Zhuang overfulfill the plan throughout the day?
壮壮计划一天练习写30个汉字，实际上午完成了计划的(7/15)，下午完成了计划的(11/15)．壮壮全天超额完成了计划的几分之几？
<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">11 / 15</gadget>
<output>11/15 = around 0.733333</output>

<gadget id="calculator">(11/15) - 1</gadget>
<output>-4/15 = around -0.266667</output>

<gadget id="calculator">(7/15) + (-4/15)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>