There is a pile of cement with trapezoidal sides. There are 16 packs on the top layer and 34 packs on the bottom layer. There are 19 layers in total (the difference between two adjacent layers is one pack). How many bags are there in this pile of cement?
有一堆水泥，侧面形如梯形，最上层放16包，最下层放34包，共有19层(相邻两层相差一包)．这堆水泥共有多少包？
<gadget id="calculator">16 + 34</gadget>
<output>50</output>

<gadget id="calculator">19 / 2</gadget>
<output>19/2 = around 9.5</output>

<gadget id="calculator">50 * (19/2)</gadget>
<output>475</output>

<result>475</result>