There are two cylindrical buckets, A and B. The height of bucket A is half that of bucket B. The diameter of the bottom of bucket A is twice that of bucket B. The volume of bucket A is 40 liters. How many liters is the volume of bucket B?
有甲、乙两个圆柱形水桶，甲水桶的高是乙水桶的一半，甲水桶的底面直径是乙水桶的2倍，甲水桶的容积是40升，乙水桶的容积是多少升？
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>