There are 4 classes in the third grade, and a total of 490 trees are planted. Three of the classes plant 127 trees each. How many trees are planted in the fourth class?
三年级有4个班，共植树490棵，其中三个班各植树127棵，第四个班植树多少棵？
<gadget id="calculator">127 * 3</gadget>
<output>381</output>

<gadget id="calculator">490 - 381</gadget>
<output>109</output>

<result>109</result>