A magic triangle has three numbers on each side.
The three numbers on each side always add up to the same sum.
We call this same sum the target sum.
It is shown above the triangle (for example: sum = 10).
Example: Target sum 10
The three corners hold 1, 2 and 3.
On each side, one number in the middle is still missing.
Left side: 1 and 2 are already there, 7 is missing (1 + 7 + 2 = 10).
Right side: 2 and 3 are there, 5 is missing (2 + 5 + 3 = 10).
Bottom side: 3 and 1 are there, 6 is missing (3 + 6 + 1 = 10).
The numbers filled in show the solution.
Example
For parents
What does this exercise practice?
Arrange numbers so every side adds up to the same sum, practising clever addition and completion.
Common pitfalls
Children often work out only one side and forget that all three sides need the same sum. Help: check each side separately and compare.
How to practice at home
Lay out three small cards as corners, then fill the sides with more cards until every side adds up the same. Building blocks make trying it out easier.
Related: Magic square, Calculation, Number house