so this is how i learned it. you have to remember a=part p=percent and w = whole. so you set it up like this a=p*w so "a" in this case is 48 and "w" is 120 (two hours) so now you substitute 48=p*120, now you have to divide each side by 120. 48/120=0.4 so 0.4=p BUT now you have to multiply by 100 for the percent