A swimming pool is 60 meters long and 10 meters wide. After expansion, the length remains the same, but the width increases to 15 meters. After the expansion, the area of the swimming pool increases by how much?
某游泳池长60米，宽10米，扩建后长不变，宽增加到15米，扩建后的游泳池面积比原来增加了百分之几？
<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">60 * 5</gadget>
<output>300</output>

<gadget id="calculator">60 * 10</gadget>
<output>600</output>

<gadget id="calculator">300 / 600</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>