Table: 1/2 hour = 15 pages read
1 hour = 30 pages read
1 1/2 hours = 45 pages read
2 hours = 60 pages read
Ruth can read 15 pages in 30 minutes. She decides to create a table to keep track of her progress. From the data provided, at what ratio is the constant of proportionality?
2,60
1,30
1/2,15
15,30