Week beginning Feb 18th – Year 3 to Year 6
Magic Crosses
Here are pictures of two crosses:
 |
 |
What do you notice about the two crosses?
What is the same?
What is different?
Both crosses use the digits 1, 2, 3, 4, and 5.
The left cross has a horizontal total of 12 and a vertical total of 6.
The right cross has a horizontal total of 8 and a vertical total of 8.
We call the cross on the right a magic cross, because its horizontal total is equal to its vertical total.
Can you find any more magic crosses using the digits 1, 2, 3, 4 and 5?
Can you find all the possibilities?
We were not able to make magic crosses using 2 or 4 in the middle. These even numbers were not possible because you were left with three odd numbers and one even. We could not make pairs of numbers from these that were either two odds or two evens.
To make a magic cross, once you have removed/chosen your center number, you need an equal number of even and odd numbers remaining.
we found these crosses.
1 at the center = 2+1+5 and 3+1+4 (totals 8)
3 at the center = 5+3+1 and 2+3+4 (totals 9)
5 at the center = 1+5+4 and 3+5+2 (totals 10)