In "Arbor Day", the students of Hongdu Primary School planted trees on a rectangular piece of land with a length of 42 meters and a width of 15 meters. If one tree is planted every 3 square meters, how many trees can be planted in total?
"植树节"中，红都小学的同学们在一块长是42米，宽是15米的长方形土地上种树，如果每3平方米种一棵树，一共可以种多少棵树？
<gadget id="calculator">42 * 15</gadget>
<output>630</output>

<gadget id="calculator">630 / 3</gadget>
<output>210</output>

<result>210</result>