A and B are two cylindrical oil barrels. A barrel holds 60kg. The height of B barrel is twice that of A barrel, and the bottom diameter is (1/2) that of A barrel. How much oil can B barrel hold?
甲、乙两个圆柱形油桶，甲桶盛60kg，乙桶的高是甲桶的2倍，底面直径是甲桶的(1/2)，乙桶可装油多少kg．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">60 * (1/2)</gadget>
<output>30</output>

<result>30</result>