To make a pair of cylindrical tin buckets without a cover, the radius of the bottom surface is 2.5 decimeters, and the height is 5 decimeters. How many square decimeters of iron sheets are needed?
做一对无盖的圆柱形铁皮水桶，底面半径是2.5分米，高5分米，大约需要铁皮多少平方分米？
<gadget id="calculator">2 * 3.14 * 2.5 * 5</gadget>
<output>78.5</output>

<gadget id="calculator">2.5 ** 2</gadget>
<output>6.25</output>

<gadget id="calculator">3.14 * 6.25</gadget>
<output>19.625</output>

<gadget id="calculator">78.5 + 19.625</gadget>
<output>98.125</output>

<result>98.125</result>