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 in the top layer and 12 steel pipes in the bottom layer. There are 7 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7层，这堆钢管共有多少根．
<gadget id="calculator">2 + 12</gadget>
<output>14</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">14 * (7/2)</gadget>
<output>49</output>

<result>49</result>