What is composing and decomposing numbers?Learning about numbers and the way they work together is an incredibly important skill that helps advance students in their math thinking. Children need to be flexible with breaking apart numbers and seeing them as a whole. Being flexible with building numbers and breaking numbers apart is called composing and decomposing numbers numbers.
Children need to be automatic with composing and decomposing numbers in the ranges 1-5, 6-10, and 10-20. Flexibility in the 1-20 range will help build success with addition, subtraction, multiplication, and division.
One of the first steps to becoming flexible with numbers is the ability to look at an amount of dots (such as on dice, dominoes or playing cards) and immediately see the pattern, and name the number represented without counting. This is called subitizing.
Subitizing activities help students begin to group numbers, add numbers and learn the combinations of different numbers. For example, children will look at a 6 and be able to recognize it as 5 and 1, 4 and 2, or 3 and 3.
As children apply this knowledge they will begin to develop more efficient strategies for solving addition and subtraction task by moving from unitary (count by 1) strategies to composite (non-count by 1) strategies. An example would be 23-6. Rather than counting back by 1's to solve the problem, a child could automatically break apart the 6 into 3 and 3, allowing a possible strategy to be 23-3 equals 20. Then 20-3 equals 17, by applying the knowledge of 10-3 equals 7.
Visualization is an important part of developing flexibility with number structure. For this reason, children will benefit from frequently working with spatial patterns (dice or dominoes), dot cards, and ten frames.
To play games that help develop composing and decomposing skills, check out the 'Math Games' link found on the left side of this page.