The school playground used to be 30 meters long and 28 meters wide. Later, it was rebuilt. The length of the playground increased by 10 meters, but the area remained the same. What is the width of the playground now?
学校的操场原来长30米，宽28米，后来进行改建，操场的长增加了10米，面积不变，现在操场的宽是多少米？
<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<gadget id="calculator">28 / 40</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">30 * (7/10)</gadget>
<output>21</output>

<result>21</result>