Answer
113
Work Step by Step
Applying the Pythagorean Theorem:
$$ 6400^2+d^2=\left(6400+1\right)^2\\ 0960000+d^2=40972801 \\ d^2=12801 \\ d=113$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.