There are 4 steel pipes in the top layer, 16 steel pipes in the bottom layer, and 7 layers. How many steel pipes are there in total?
一堆钢管，最上层有4根，最下层有16根，有7层，这堆钢管一共多少根．
<gadget id="calculator">4 + 16</gadget>
<output>20</output>

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

<gadget id="calculator">20 * (7/2)</gadget>
<output>70</output>

<result>70</result>