Rina is a hard-working college freshman. One Sunday, she decides to work nonstop until she has answered 150 practice problems for her economics course. She starts work at 8:00 AM and uses a table
to keep track of her progress throughout the day. She notices that as she gets tired, it takes her longer to
solve each problem.
Time
8:00 AM
9:00 AM
10:00 AM
11:00 AM
Noon
Total Problems Answered
0
60
105
135
150
Use the table to answer the following questions.
The marginal, or additional, gain from Rina's second hour of work, from 9:00 AM to 10:00 AM, IS
problems.
The marginal gain from Rina's fourth hour of work, from 11:00 AM to noon, is problems.
Later, the teaching assistant in Rina's economics course gives her some advice. "Based on past
experience," the teaching assistant says, "working on 52.5 problems raises a student's exam score by
about the same amount as reading the textbook for 1 hour." For simplicity, assume students always cover
the same number of pages during each hour they spend reading.
Given this information, in order to use her 4 hours of study time to get the best exam score possible, how
many hours should she have spent working on problems, and how many should she have spent reading?
0 hours working on problems, 4 hours reading
1 hour working on problems, 3 hours reading
2 hours working on problems, 2 hours reading
4 hours working on problems, 0 hours reading