A cylindrical bucket contains 20 liters of water, accounting for (4/7) of the volume of the bucket. It is known that the height of the bucket is 3.5 decimeters. What is the area of the bottom of the bucket?
一个圆柱形水桶，里面装有20升水，占水桶容积的(4/7)，已知水桶高3.5分米，水桶的底面积是多少？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">20 / (4/7) / 3.5</gadget>
<output>10</output>

<result>10</result>