In the Department of Mathematical and Computational Science, 83% of lecture halls have chalk¬boards, and the other 17% have dry-erase boards. Of the classes taught in rooms with chalkboards, 75% are mathematics courses, 15% are computer sci¬ence courses, and 10% are statistics courses. Of the classes taught in rooms with dry-erase boards, 65% are computer science courses, 8% are mathemat¬ics courses, and 27% are statistics courses. What percentage of courses at the college are mathematics or statistics?