In a calculation square there are nine numbers in three rows and three columns.
At the edge are the sums, so what each row and each column add up to.
Some cells are empty. You are to find the missing numbers.
Example:
First row: 5 + 8 + ? makes 16. The 3 is missing, because 5 + 8 + 3 = 16.
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.
The numbers written in show the answer.
Example
For parents
What does this exercise practice?
Determine missing addends using row and column sums and practice bundling numbers.
Common pitfalls
Children sometimes add up all three fields even though one is still empty. Tip: first find the row where only one number is missing, then work it out.
How to practice at home
Lay out three rows of building blocks, count each row and each column. Cover one stack and have the missing amount guessed.
Related: Magic Square, Arrow arithmetic, Math Table