Teacher Wang asked the students to explore the calculation method of the area of a circle in groups. Shen Lan divided a circle into several equal parts, cut them along the radius and assembled them into an approximate rectangle. The width of the rectangle was measured to be 5 cm. What is the area of the circle in square meters? centimeter.
王老师让同学们分小组探究圆的面积计算方法，沈岚将一个圆分成若干等份，沿半径剪开拼成一个近似长方形，量得长方形的宽是5厘米，这个圆的面积是多少平方厘米．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>