Kathy read 4 books in 1 h 46 min. She took the same amount of time to read each of the first 3 books. She took 46 min longer to read the fourth book than each of the first 3 books. She finished reading all the books at 21 37. What time did she start reading the fourth book?
Duration that Kathy took to read the first book = 1 u
Duration that Kathy took to read the second book = 1 u
Duration that Kathy took to read the third book = 1 u
Duration that Kathy took to read the fourth book = 1 u + 46 min

Total duration that Kathy took to read the four books 
= 1 u + 1 u + 1 u + 1 u + 46 min
= 4 u + 46 min

4 u + 46 min = 1 h 46 min
4 u = 106 min - 46 min
4 u = 60 min  

1 u = 60 min ÷ 4 = 15 min

Duration that Kathy took to read the fourth book
= 15 min + 46 min
= 61 min
= 1 h 1 min

1 h 1 min before 21 37: 20 36

Time that Kathy started to read the fourth book = 20 36

Answer(s): 20 36