Grandpa, grandma, father, mother and I want 5 cakes in total. You can only bake two sheets at a time, and both sides must be baked, and each side takes 3 minutes. In order to let everyone eat the cake as soon as possible, how do you think the pancake should be? How many minutes is the minimum? (Consider the time needed.)
爷爷、奶奶、爸爸、妈妈和我一共要5张饼．每次只能烙两张两面都要烙，每面需要3分钟．为了使大家尽快吃上饼，你认为应该怎样烙饼？最少需要多少分钟？(算需要的时间．)
<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>