A pile of steel pipes is piled up in a trapezoidal shape. There are 2 steel pipes on the top layer and 6 steel pipes on the bottom layer. There are 5 layers in total. How many steel pipes are there in this pile?
一堆钢管堆成梯形，顶层有2根，底层有6根，共5层，这堆钢管共有多少根．
<gadget id="calculator">2 + 6</gadget>
<output>8</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">8 * (5/2)</gadget>
<output>20</output>

<result>20</result>