It wasn't until the middle of chapter 5 that I realized that, in our Intro Number Theory AoPS book, the answers to the grey "teaching problems" are not fully worked. At least, many many are not fully worked. Which means: if a problem has subsets, as in

a. part #1

b. part #2, relies on solution to part #1

c. part #3, relies on solution to part #2

d. Big Scary Problem that isn't so hard if you have worked out how to do a-c

The solution is worked to the Big Scary Problem, but if you are stuck back at (a) or (b) or ( c) there's nothing for you, and to figure it out requires understanding the full solution to (d). Which makes this book not so easy for us to use.

Algebra didn't do this -- it had solutions for each part of the grey problems -- and the Counting/Probability doesn't. Now I know why Number Theory is less popular with the children than C&P!!! But I've not heard of this problem. Has no one else found it an obstacle?

**Edited by serendipitous journey, 10 October 2017 - 07:50 PM.**