dots in the array

[sanju09]

All the dots in the array are 2 units apart vertically and horizontally. What is the length of the longest line segment that can be drawn joining any two dots in the array without passing through any other dot?
A. 2
B. 2√2
C. 3
D. √10
E. √20

[spoiler]Source: majortests.com[/spoiler]

[kvcpk]

Jon the edge dot and the middle dot of the opposite side.

sqrt(4^2 + 2^2) = sqrt(20)

pick E

[selango]

Pick E

[Brent@GMATPrepNow]

All the dots in the array are 2 units apart vertically and horizontally. What is the length of the longest line segment that can be drawn joining any two dots in the array without passing through any other dot?
A. 2
B. 2√2
C. 3
D. √10
E. √20

[spoiler]Source: majortests.com[/spoiler]

The longest line segment it's created when we connect points on opposite sides of the diagonal.

HOWEVER, this does not meet the condition that the line cannot pass through any other point

So, the next longest line segment looks something like this:


Since we have a right triangle, we can apply the Pythagorean theorem to write: 2² + 4² = x²
Simplify: 20 = x²
Solve: x = √20

Answer: E

Cheers,
Brent