A number square has numbers in rows and columns.
On the right and at the bottom it says what each row and each column adds up to.
Some fields are empty. Find the missing numbers so that all the sums are right.
Small square: at the top left is 4, at the bottom left 5, at the bottom right 3.
The top row should make 10. What is missing at the top right?
4 plus 6 makes 10, so the 6 belongs in the empty field.
Big square: in the first row 5 + 8 + ? makes 16. The 3 is missing, because 5 + 8 + 3 = 16.
In the first column 5 + 6 + ? makes 16. The 5 is missing, because 5 + 6 + 5 = 16.
Always carry on where only one number is still missing.
Then check: the columns have to give their sums as well.
The numbers filled in show the solution.
Examples
Example: Completing squares
Example: Big number square
For parents
What does this exercise practice?
Complete numbers in a grid so that the row and column sums fit. That practices plus, minus and checked trial and error; the big square adds bundling three addends.
Common pitfalls
Some children look at only one sum. What matters is that the number found fits in both directions, in its row and in its column. In the big square it helps to look for the row where only one number is missing first.
How to practice at home
Build a small two-by-two grid with building blocks and count the rows and columns together. For the big square lay out three rows, cover one stack and have the missing amount guessed.
Related: Arrow arithmetic, Math Table, What does multiplying mean?