Divided by 9, the remaining six are: 150, 156, 162, 168, 174, 180, 186,/.

Divided by 6, the remaining 3 are: 153, 156, 159, 162, 165, 168,17/kloc. The same numbers in the three categories are 174 and 192.

So in the fifth grade, 174 or 192 people went to plant trees.