A rectangle has a length of 10dm and a width of 5dm. The perimeter of the square is the same as the perimeter of the rectangle. What is the area of the square?
一个长方形长10dm，宽5dm，正方形的周长和长方形的周长一样，这个正方形的面积是多少？
<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">30 / 4</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">(15/2) * (15/2)</gadget>
<output>225/4 = around 56.25</output>

<result>225/4 = around 56.25</result>