For a rectangular fish pond with a length of 12 meters and a width of 8 meters, a pillar is inserted every 4 meters around it, and all four corners must be inserted. How many pillars are needed in total?
一个长12米，宽8米的长方形鱼池，在它四周每隔4米插一柱子，四个角都要插，一共需要多少根柱子？
<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 * (1/2)</gadget>
<output>10</output>

<result>10</result>