The Pythagorean theorem is what is most useful here, and a calculator; for the following...
Imagine forming a triangle by creating that last leg between the starting position and the ending position; the length of that side will be our missing variable "y".
600² + 800²= y²
The sum of the two (600² & 800²) must then be square rooted to find the length
y² = 1,000,000 and the square root of y²= 1,000 (YOUR ANSWER) "y"
