Comment
There is no exact answer to this. It will have to shown in terms of the width. Also we need to use the Pythagorean Formula
Givens
L = 10 * W
W = W
Formula
L^2 + W^2 = C^2
Solution
(10W)^2 + (W^2) = C^2
C^2 = 100W^2 +W^2
C^2 = 101W^2 Now take the square root.
C = sqrt(101W^2)
C= W*sqrt(101) <<<<< Answer. I think this is what they mean