There are a pile of steel pipes on the construction site. The cross section is a trapezoid. It is known that there are 2 steel pipes on the top layer and 12 steel pipes on the bottom layer. There are 11 layers in total. How many steel pipes are there in this pile?
工地上有一堆钢管，横截面是一个梯形，已知最上面一层有2根，最下面一层有12根，共堆了11层，这堆钢管共有多少根．
<gadget id="calculator">2 + 12</gadget>
<output>14</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">14 * (11/2)</gadget>
<output>77</output>

<result>77</result>