Question

2. How many right triangles with distinct sizes have all three vertices taken from the array of dots below? Two triangles are to be considered distinct if their side lengths are not the same 3 lengths.
. . . . . .
. . . . . .
. . . . . .
. . . . . .

Answer 1

the array is 4x6, so just think of the possible rectangles that fit in there:
1x1
1x2
...
4x6