A pan can bake up to 2 cakes at a time, and both sides must be baked for 3 minutes on each side. How many minutes does it take to bake 5 pancakes?
一只平底锅上每次最多能烙2张饼，两面都要烙，每面3分钟．烙5个饼至少需要多少分钟．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<result>15</result>