Subtraction continues to be a challenge for many students.
Why? The skill of subtraction is very different from addition because in addition there are no “invisible” numbers, all of the values are represented, the students just have to count all of the numbers. In order to subtract accurately, students have to be aware of the “invisible” numbers inside of other numbers. Students must know for example, that when subtracting 14 – 8 that within 14 there is also an invisible ” 6.” Most students are unclear of all of the numbers embedded within another. In order for a student to successfully subtract numbers less than 10 they must know all of the numbers that are embedded within 10 i.e., 9, 8, 7, 6 , 5, etc. and in order to successfully subtract numbers from 20 then students must know all of the numbers embedded within 20 i.e., 19, 18, 17, 16, etc.This is a skill called hierarchical inclusion and it can only be developed through counting, counting, counting. Unfortunately, most students have limited opportunities to count, especially the counting of objects which is so crucial for strong number sense. In addition, most primary grade textbooks focus very few of their pages on counting.
If you want your child to become stronger at subtraction, give them objects to count both forward and backwards. Once a student has developed the ability to count by ones forward, ask them to practice counting the same amount backwards. Once they can count by ones going forward and backwards ask them to practice counting objects forward and backwards by tens. In virtual math classes, individual Jamboards can be created for students to touch and count, cross off and count, or circle and count forward and backwards. Providing this in class counting practice can be crucial for students with limited home support and can provide a lot of insight into their thinking.