Knowing addition facts is extremely important. Students who struggle with addition facts also struggle with the linked concepts, such as subtraction, word problems, addition with bigger numbers, etc. Add using doubles facts worksheet is a great way to help learners become fluent with addition facts. In this worksheet, students practice solving problems written in the horizontal format. How numbers are laid out in a problem affects the method a student employs to solve it. Therefore to develop actual fluency and mastery of multiple strategies, students must practice different formats.