Plant trees around a rectangular field that is 80 meters long and 60 meters wide, and plant trees every 4 meters. How many trees should be planted in total?
在一块长80米，宽60米的长方形地的周围种树，每隔4米种一棵，一共要种多少棵？
<gadget id="calculator">80 + 60</gadget>
<output>140</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">140 * (1/2)</gadget>
<output>70</output>

<result>70</result>