Addition of doubles quiz online for kids in kindergarten, 1st , 2nd and 3rd grades. Adding doubles simply means adding a number twice. For example, 5 + 5, 6 + 6 etc. Adding a number twice is like multiplying that number by two. In this quiz, children will master their addition skills required in the above mentioned grades. Teachers can use this exercise to review with kids while at home or in school. Have fun learning and review until the skill is mastered.