A rectangular pond is 100 meters long and 40 meters wide, and a tree is planted every 2 meters beside the pond. How many trees should be planted in total?
一个长方形的池塘长100米，宽40米，在池边每隔2米种一棵树，一共需要种多少棵树．
<gadget id="calculator">100 * 2</gadget>
<output>200</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<gadget id="calculator">200 + 80</gadget>
<output>280</output>

<gadget id="calculator">280 / 2</gadget>
<output>140</output>

<result>140</result>