If an addend is missing, students use the count-on method or the relationship between addition and subtraction to determine the missing number. Also, they add the addends if the missing number is the sum of the addition sentence. This worksheet, add 2-digit numbers and multiples of 10, offers a tonne of practice with this idea. As the worksheet uses the column method, it is helpful in getting students toward higher accuracy, especially with bigger numbers and in scenarios where regrouping is required.