To bake 5 cakes, one pan can only bake 2 cakes at a time, both sides must be baked, each side needs 3 minutes, how many minutes is the minimum time to bake 5 cakes.
要烙5张饼，一口平底锅一次只能烙2张，两面都要烙，每面需要3分钟，最少需要多少分钟能烙好5张饼．
<gadget id="calculator">3 * 2</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>