A cylindrical oil barrel is full of oil, pour out (3/4) the oil in the barrel, there are 20 liters left, the height of the oil barrel is 8 decimeters, what is the area of the bottom of the oil barrel in square decimeters?
一个圆柱形油桶，装满了油，把桶里的油倒出(3/4)，还剩20升，油桶高8分米，油桶的底面积是多少平方分米？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / (1/4) / 8</gadget>
<output>10</output>

<result>10</result>