On the Arbor Day, the fifth and sixth grade students of Chunyang Primary School participated in the tree planting activity. The students in the fifth grade planted 230 trees, and the number of trees planted by the students in the sixth grade was 45 times less than that in the fifth grade. How many trees were planted in the sixth grade?
植树节，纯阳小学五、六年级的同学参加植树活动．五年级的同学植树230棵，六年级的同学植树的棵数比五年级的3倍少45棵，六年级植树多少棵？
<gadget id="calculator">230 * 3</gadget>
<output>690</output>

<gadget id="calculator">690 - 45</gadget>
<output>645</output>

<result>645</result>