A sow gave birth to 12 piglets, the first 6 pigs weighed exactly 3.5 kg each, the last 3 pigs weighed 3 kg each, and the last 3 pigs weighed 2 kg each. So, how many kilograms does this group of baby pigs weigh on average?
有一头母猪产下12头猪娃，先产下的6头恰好每头都重3.5千克，后产下的3头每头都重3千克，最后3头每头都重2千克．那么，这群猪娃平均每头重多少千克？
<gadget id="calculator">3.5 * 6</gadget>
<output>21</output>

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

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">21 + 9 + 6</gadget>
<output>36</output>

<gadget id="calculator">36 / 12</gadget>
<output>3</output>

<result>3</result>