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 unit rate (constant of proportionality) represented?
Time (hours) Pages read
1/2, 1, 1 1/2, 2 / 15, 30, 45, 60
(2, 60)
(1, 30)
(1/2, 15)
(15, 30)