Average reading speed means nothing: you have to add time to write comments in the margins and mark up the paper, you read more slowly when you're grading, often you're working with hard-to-read handwriting, and math problems (show your work!) take time to go through and debug, especially if you're giving partial credit (suppose I make a mistake at step 2 but the rest of my answer is logically consistent with that mistake...).
One one page typed essay assignment per week? I had 5 page papers, 20 page term projects, weekly quizzes in class, exams, 30 math problems once or twice a week, labs.
Of 30 math problems about five would be randomly selected and checked. 30 seconds on average to check a problem on your class size assumptions is about 5 hours a week (this is an average between about 10 seconds for someone who gets it right and 1-2 minutes for someone who makes some amount of mistakes and needs careful correction). Then you have quizzes and exams: let's amortize that to about 10 questions per week, and you need to carefully inspect them for partial credit. That's another 20 hours a week (let's say you take a full minute per problem). That's 25 hours a week to grade math.
One one page typed essay assignment per week? I had 5 page papers, 20 page term projects, weekly quizzes in class, exams, 30 math problems once or twice a week, labs.
Of 30 math problems about five would be randomly selected and checked. 30 seconds on average to check a problem on your class size assumptions is about 5 hours a week (this is an average between about 10 seconds for someone who gets it right and 1-2 minutes for someone who makes some amount of mistakes and needs careful correction). Then you have quizzes and exams: let's amortize that to about 10 questions per week, and you need to carefully inspect them for partial credit. That's another 20 hours a week (let's say you take a full minute per problem). That's 25 hours a week to grade math.