Math Mammoth Decimals 2 is a book about decimal place value and the four operations with decimals. Its content matches fifth grade standards, but the book is useful for anyone who needs to learn these topics and who has the sufficient foundation (of approximately 4th grade math). The book starts out with the topics of place value and decimals on a number line. Then students solve sums, such as 0.8 + 0.06, using mental math and their knowledge of place value. Adding and subtracting decimals in columns comes next. Students also learn to compare and round decimals. Then we study multiplying and dividing decimals by whole numbers, both using mental math, and using multiplication in columns, and long division. Multiplying and dividing decimals by powers of ten is presented with the help of place value charts. Next, we study how to multiply decimals by decimals. Students are encouraged to use estimation in decimal multiplications. They also solve problems connected to real life, learn about multiplication as scaling, and practice decimal divisions that can be done with mental math. Then we study the metric system and how to convert various metric units. After that, we turn our attention to dividing decimals by decimals, which then completes our study of all decimal arithmetic. Lastly, students practice measurement conversions within the customary system and do some generic problem solving involving decimal numbers. After studying Math Mammoth Decimals 2, the student should understand how to perform all four operations with decimals. However, please note that the lessons here don't offer practice for these operations with decimals that have more than three decimal digits. We offer just that in the book Math Mammoth Fractions & Decimals 3, intended for 6th grade or higher. The answers are appended.