Question

film processor can develop 100 negatives in 5 minutes how many minutes will it take to develop 1200 negatives?

Answer 1

100 negatives are made in 5 mins
so 1 negatives are made in 5/100 mins
so 1200 negatives are made in 5x1200/100 mins = 60 mins = 1 hr

Answer 2

100 negatives are made in 5 mins

So 1 negatives are made =  5/100 mins

Now A.T.Q

1200 negatives are made =
                                     =    5x1200/100 mins
                                     =     6000/100 mins
                                     =     60 minutes

Or 1 hour.