If 20 volunteers can wash 100 cars in 2.5 hours, find the constant of variation and find out how many cars 30 volunteers can wash in 3 hours?

20 volunteers......100 cars...........2,5 h
1 volunteer............100 cars..........2,5*20=50 h
1  volunteer...........100:50=2 cars...........1h
1 volunteer...............2*3=6 cars...............3h
30 volunteers.........6*30=180 cars............3h

Answer: 180 cars