Mom wants to bake 9 cakes, but only two cakes can be baked at a time, and both sides need to be baked, each side takes 3 minutes, at least how many minutes will it take to cook these 9 cakes.
妈妈要烙9张饼，每次只能烙两张，两面都要烙，每面3分钟，至少需要多少分钟才能烙熟这9张饼．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 * 2 * 3</gadget>
<output>18</output>

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

<gadget id="calculator">18 + 9</gadget>
<output>27</output>

<result>27</result>