The second main idea is how to read and write decimals. You start by writing the whole number first if there is one and when you get to the decimal point you write and unless it is just a decimal. After you get there the back half starts with tenths and goes on from there by a place value of ten make sure to add the ths on the end. The same rules apply when reading a decimal. For example, 34.23 so you would write it like thirty-four and Twenty- three hundredths. When reading a decimal you just right it down in the right place values for example, Three and twenty-one hundredths would look like 3.21. As a future teacher, I think this is an important concept for students to learn at a young age because the sooner they start learning to write