The school divided the task of planting a batch of trees among grades four, five, and six according to the ratio of 3:4:5. The fifth grade planted 40 trees. How many trees are there in total?
学校把植一批树的任务按3：4：5分给四、五、六三个年级，五年级植了40棵，这批树共有多少棵？
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">10 * 12</gadget>
<output>120</output>

<result>120</result>