To bake a cake on the stove, both sides of the cake must be baked, each side takes 3 minutes, and only 2 cakes can be placed on the stove at the same time, now 3 cakes need to be baked, how many hours will it take at least.
在火炉上烤饼，饼的两面都要烤，每烤一面要3分钟，炉上只能同时放2块饼，现在需要烤3块饼，至少需要多少小时．
<gadget id="calculator">3 + 3 + 3</gadget>
<output>9</output>

<gadget id="calculator">9 / 60</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>