Determine the magic sum from a magic square

Determine for a magic square of order n, the magic sum m. For example m=15 for a magic square of order 3.

For this problem I wrote:

m = sum(n)

This gave me 15 15 15. Why is this not correct?

I then tried

m = sum(n(1, :))

This gave me 15. Why is this not correct?

I don't understand why my answer is not accepted. This is for Cody Problem 1087: Magic is simple (for beginners).

[David Goodmanson]

Hi Farook,

It looks like you are given the size of the magic square, but not the magic square itself. So if all you are given is that the magic square is 3x3, how do you obtain 15 from n=3?

Answer 1

[Davide Masiello]

I think you are inputting the magic square itself to your function, rather than its order.

I believe the relation between a magic square order (n) and the magic sum (S) is

So your function should be

function out = magic_sum(n)
out = n*(n^2+1)/2
end

[Farooq]

Thank you for your help!

[Nathan Hardenberg]

While the formula is a valid solution I think the intended way is to sum up one colum or row, since all rows/colums and diagonals do sum up to the same number:

mag_sqr = magic(3)

mag_sqr = 3×3

8 1 6 3 5 7 4 9 2

sol1 = sum(mag_sqr(:,1))  % sum up first colum

sol1 = 15

sol2 = sum(mag_sqr(1,:))  % sum up first row

sol2 = 15