11. (10 points) Several people completed the task of planting 2013 trees, with each person planting the same number of trees. If 5 people did not participate in planting, the rest would need to plant 2 more trees each to fail to complete the task, while planting 3 more trees each would exceed the task. How many people participated in planting?


【Analysis】According to the time, "several people completed the task of planting 2013 trees, with each person planting the same number of trees," then the number of people and the number of trees are factors of 2013. Let's assume there were originally $a$ people, and each person planted $b$ trees, then $a b=2013$. Since 5 people did not participate in planting, $a>5$. "If 5 people do not participate in planting, the rest of the people planting 2 more trees each cannot complete the task, while planting 3 more trees each can exceed the task." Then $2(a-5)<5b<3(a-5)$
$2(a-5) \div 5 < b < 3(a-5) \div 5$
$b$ is around $0.5(a-5)$
$2013=33 \times 61$ fits
$a=61, \quad b=33$
A total of 61 people participated in planting trees.
Answer: A total of 61 people participated in planting trees.