Later, the teaching assistant in Caroline’s chemistry course gives her some advice. “Based on past experience,” the teaching assistant says, “working on 15 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?

1 hour working on problems, 3 hours reading
2 hours working on problems, 2 hours reading
3 hours working on problems, 1 hour reading
4 hours working on problems, 0 hours reading

“working on 15 problems raises a student’s exam score by about the same amount as reading the textbook for 1 hour.” we can develop the following expression:

For raising the score: 15 problems = 1 hour reading

Because we do not know how much time each problem takes, She should have spent 1 hour working on problems and 3 hours reading (maximum).

For giving an example, let's consider you spent 20 minutes on each problem, then in 1 hour you would have resolved only 3 problems. That is way, she must spend the maximum of hours reading.