A circular tabletop with a diameter of 80 cm, now a glass of the same size should be placed on the tabletop, find the area of the tabletop glass. If the price of glass is 100 yuan per square meter, how much does the glass cost?
一个圆形的桌面，直径为80厘米，现在要在桌面上安放一个同样大小的玻璃，求这个桌面玻璃的面积．如果玻璃每平方米价格为100元，这个玻璃要花多少钱？
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 ** 2</gadget>
<output>1_600</output>

<gadget id="calculator">1_600 / 10_000</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">3.14 * (4/25) * 100</gadget>
<output>50.24</output>

<result>50.24</result>