Students in class 5 and 2 planted trees, planted 8 trees in 0.2 hours, and planted 40 trees per hour on average. How many minutes did it take on average to plant a tree?
五2班同学植树，0.2小时植树8棵，平均每小时种树40棵，种一棵树平均用多少分钟．
<result>1.5</result>