During the tree-planting activities on Arbor Day, a group of trees were allocated to grades four, five, and six at a ratio of 1:2:7. The sixth grade planted 150 more trees than the fifth grade. What is the total number of trees in this batch?
植树节开展植树活动中，把一批树按1：2：7分配给四、五、六三个年级，六年级比五年级多植了150棵树．求这批树的总数是多少？
<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">150 / 5</gadget>
<output>30</output>

<gadget id="calculator">1 + 2 + 7</gadget>
<output>10</output>

<gadget id="calculator">30 * 10</gadget>
<output>300</output>

<result>300</result>