In a pile of steel pipes, there are 18 at the bottom and 6 at the top, and there is a difference between two adjacent floors. How many steel pipes are there in this pile?
一堆钢管，最底层有18根，最高层有6根，每相邻的两层相差一根，这堆钢管共有多少．
<gadget id="calculator">6 + 18</gadget>
<output>24</output>

<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<gadget id="calculator">13 / 2</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">24 * (13/2)</gadget>
<output>156</output>

<result>156</result>