Understanding the one-to-one correspondence of object to object is necessary before young children can carry out meaningful counting and higher calculations. Children can find many opportunities in their daily life to experience one-to-one correspondence.
They can place one sock inside one shoe or one shoe on one foot; they can get one napkin or snack for each member of the family or class; they can place one lid on each of several containers; they can place pieces in one-piece puzzles. Once children understand these relationships, they can link one number with one object and then count with understanding.
When students are ready to develop the skill of counting, they can benefit from learning several counting strategies to increase their accuracy and efficiency. Students sometimes develop one or more such strategies on their own, but it is to their benefit to provide training in this area.
As with any concepts or skills, it is important to start working with real objects and manipulatives and to continue providing these as learning aids. For this particular activity, we placed a predetermined number of leaves on four different carrots. We practiced adding and subtracting the various leaves, noticing the changes in quantity.