$3 \times 8$ Array Problem: Finding the Longest Line Containing Exactly 3 Dots

Question

In the $3 \times 8$ array, the dots are evenly spaced horizontally and vertically with each dot 1 cm from the nearest neighboring dots. In simplest radical form, what is the number of units in the length of the longest segment containing exactly 3 dots, two of which are the segment's endpoints?

Answer 1

Does the below figure help at all?