It takes 6 minutes to bake a piece of bread (3 minutes for each side), and an oven can bake 4 pieces of bread at the same time, so how many minutes is the minimum time for 6 pieces of bread?
烤一个面包需要6分钟(正、反两面各需要3分钟)，一个烤箱每次可以同时烤4个面包，那么，6个面包最少需要多少分钟．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>