The iron sheet is used to make cylindrical oil drums. If only the sides are used, 20 can be made. If only the bottom surface is used, 60 can be made. How many gasoline drums can be made from this sheet of iron sheet?
铁皮做圆柱形的油桶，如果只做侧面，可以做20个，如果只做底面，可以做60个，这张铁皮最多可以做多少个汽油桶．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/60) * 2</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<result>12</result>