Firstly, find out how many students there are in 7 batches. You can do this by timesing 48 by 7 to get 336. So there are 336 students in 7 batches. Each student does 24 hours of community service in a year so do 336 times by 24 which is 8,064. Therefore,the college contributes 8,064 hours of community service in a year.