420 miles because it’s just correct
I need to go did hehshshshshshehehehehe
To find out if the triangle is a right triangle, we must check if the following equation is true:

on the left side, we have:

and on the right side, we have:

since on both sides we get 625, we have that the brace forms a right triangle.
1 + 54 = 55
2 + 53 = 55
3 + 52 = 55
4 + 51 = 55
5 + 50 = 55
6 + 49 = 55
7 + 48 = 55
8 + 47 = 55
9 + 46 = 55
10 + 45 = 55
and so on...
I hope that helps. :)