This is well know puzzle for mathematician,

Problem is like this: arrange the number from 1 to 9 in 3X3 Grid in such from then sum of Horizontal, Vertical and Diagonal sum must be equal that is 15. Answer is given below.

Now, what will you do if number is start from 2 to 10 or 11 to 19…? Here I have showing you solution for that. Extend your Grid from 3×3 to 5×5. OK?

Refer Figure 1:

Figure 1

We are going to arrange number from 1 to 9. Write 1 to 3, 4 to 6 and 7 to 9 in diagonal foam. Shown in figure.

Here our outer number is 1, 3, 7 and 9. While already arrange number is 2,4,6,5 and 8. Now Move number 9 from its original location to its opposite number beside of 1. Refer Figure 2.

Figure 2

Perform same task for outer number 1, 3 and 7. Given in Figure 3, Figure 4 and Figure 5.

Figure 3

Figure 4

Figure 5

And finally you obtain same result as given in Figure 1 Look at the Figure 6.

Figure 6

Try it by you own with different sequence like 2 to 10, 3 to 11 etc. Only one rule apply number must be in sequence.