cylindrical barn, the radius of the base measured from the inside and the height are both 2 meters. If each cubic meter of grain weighs 400 kilograms. How many tons of grain can this grain store hold?
一个圆柱形粮屯，从里面量得底面的半径是和高都是2米．如果每立方米粮食重400千克．这个粮屯能装粮食多少吨？
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">400 / 1_000</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3.14 * 4 * 2 * (2/5)</gadget>
<output>10.048</output>

<result>10.048</result>