There is 1 monitor for every fifteen students because 30 / 2 = <<30/2=15>>15
There are 120 students because 8 x 15 = <<8*15=120>>120
60% of the lunchroom is boys because 100 - 40 = <<100-40=60>>60
There are 72 boys because 120 x .6 = <<120*.6=72>>72
There are 48 girls because 120 x .4 = <<120*.4=48>>48
The boys drink 72 cartons of milk because 72 x 1 = <<72*1=72>>72
The girls drink 96 cartons of milk because 48 x 2 = <<48*2=96>>96
They drink 168 cartons of milk because 72 + 96 = <<72+96=168>>168
#### 168