Bake cakes on the baking tray, only two sheets can be placed at a time, both sides of the cakes must be baked, each side needs to be baked for 3 minutes, at least how many minutes is required to bake 6 sheets of cakes.
在烤盘上烤饼，每次只能放两张，饼的两面都要烤，每烤完一面要3分钟，烤6张饼至少要多少分钟．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>