One of the best strategies for strengthening number sense is the use of "problem strings" which are also known as "number strings."
It can also be called "high dosage" patterning.
It essentially starts with a simple computation fact in any of the 4 arithmetic operations and numbers that the students are familiar with.
All students would be familiar with the result of the first computation.
The next computation would vary slightly and would need an understanding of the properties of the numbers as well as the operations. For example, if the first computation is 8 + 7 = 15, the next could be 9 + 7. Here one of the numbers of an addition fact has been increased by 1 and hence the result will also increase by 1! The answer would be 16.
The third computation would follow the second and would again be slightly different.
There would be 10 or 15 such computations. The entire set of computations is called a "problem string".
Problem Strings fully exploit the patterns involving numbers & their operations.
We give below a few such problem strings with explanations of the concept involved.
Prepare a word table with 4 such strings, one each for each operation, convert to png file and insert here
https://www.mathisfigureoutable.com/problemstrings