Unlike other listening books that might focus on "survival Chinese" (ordering food, taking a taxi), Book 1 is academic. It focuses on:
(Listening) series, the answers for those workbooks can be found on Scribd's answer analysis page number in this book? hanyu-tingli-jiaocheng pdf download - Cchatty
Listening to a 2-minute dialogue and then having no idea if you heard "15" or "50" is maddening. The answer key provides immediate confirmation. Without it, you cannot correct your own mistakes, which means you will repeat the same listening errors indefinitely.