This book has been very problematic for us. There are a LOT of mistakes in the answer key. I usually use the answer key to quickly check my daughter's work then have her go back and re-work missed problems so she can understand where she went wrong. Often she comes across a "missed" problem in which she cannot find her mistake. Naturally arriving at the same answer two or three times. This is when I check the book's answer key and do the math myself and then with a calculator to determine where the error is. The error is always in the answer key.
Aside from that there was an issue which I did email Spectrum about at the start of the year. The problem was in that they placed 6 problems under the heading "Multiplying and Dividing WHOLE numbers". Yet one of the problems was solved by SPECTRUM using decimals instead of simply using the remainder. How does anyone know that the books writers want a decimal to be used and then rounded up to a whole number when it is in the "Multiplying and Dividing WHOLE numbers" section? Mind you no other problem in this entire section required dividing into decimal territory and then rounding up. I did email SPECTRUM about this and that is how I discovered how they came to the mistake.
Also, the sequence is very off. It is best to lead a child through math in a way that does not confuse or put them to attempting one thing when another should be mastered first. Random bouncing around instead of a focused order in what is introduced is not conducive to understanding. I had to make a lot of adjustments in this area. It took a good deal of my time to go through each page and mark the order in which each area should be covered.
To sum it up, this book may be good for determining scope and (very loosely) sequence if you home-school your child, but do not rely on it for accuracy or appropriate flow. I have made a lot of adjustments using this book and have grown tired of the problematic answer key errors, and poor sequence. I have decided as of today that we will seek out a book which has been more carefully edited and sequenced. Do not waste your money here folks.