Give your little one the opportunity to dive deeper into addition with this add 4 within 20 worksheet. After learning how to count, students should learn how to add numbers. There is lots of practice with addition in add 4 within 20 worksheet. In each problem, the numbers are laid out in the horizontal format. Students should try to use different strategies involving composing and decomposing numbers to solve these problems. This will help them develop flexibility and fluency.