April = 6 * 30 = <<6*30=180>>180 hours
June = 5 * 30 = <<5*30=150>>150 hours
September = 8 * 30 = <<8*30=240>>240 hours
Total hours = 180 + 150 + 240 = <<180+150+240=570>>570 hours
570 hours/3 = <<570/3=190>>190 hours
He averaged working 190 hours per month.
#### 190