Taking kids from using their fingers and concrete materials to thinking abstractly about addition or using mental strategies is a massive step. When they begin to add larger numbers and cannot use concrete materials, its hard to scaffold their use of effective mental strategies – like adding 10.
The best way I’ve found to support their addition of larger numbers is by using vertical number lines. Students create their number lines to 100 and use pegs to count on, or add 10 (using the different colours) to add larger numbers together. This activity allows them to visualise and physically complete addition of larger numbers.
A fun application of the vertical numbers lines is ‘Race to 100’, where students start at 0 and roll dice to move their peg up the line. The first to 100 wins. Another alternative is ‘Race to 0’, to practice subtraction.
I have used them multiple times, for counting on, adding 10, adding to 10 and counting down. Students got use to pulling out the lines and using them to calculate addition and subtraction. Perfect for grades 1 to 3.