On Arbor Day, students in grades 5 and 6 of Experimental Primary School went to plant trees. The number of students in the sixth grade who participated in tree planting was twice that of the fifth grade. On average, each student in the sixth grade planted 4 trees, and the average student in the fifth grade planted 1 tree. How many trees are planted by each fifth and sixth grader participating in tree planting?
植树节，实验小学五、六年级学生去植树．参加植树的六年级学生人数是五年级的2倍，六年级平均每人植树4棵，五年级平均每人植树1棵．参加植树的五、六年级学生平均每人植树多少棵？
<result>3</result>