Addition of decimals quiz for students to learn online. Addition of decimals is straight forward like addition studied in the previous grades but carrying values across the decimal point is where the trick lies. Values are rounded up to one and crossed over the decimal point if they are up to or above ten. Learn to add decimals with this quiz and get feedback as you practice. This exercise falls in line with pre-algebra activities students study in 4th, 5th, 6th and 7th grades.