Workers at the forestry farm piled the 40 cut trees into a trapezoidal shape with 5 layers, with 4 trees on the top layer and how many trees on the bottom layer?
林场的工人把砍下的40棵树木堆成一个梯形的形状，堆了5层，最上一层有4根，最下一层有多少根？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 * (2/5)</gadget>
<output>16</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<result>12</result>