Which of these four sets of side lengths will form a right triangle?

set 1
10 cm, 26 cm, 24 cm

set 2
4 in., 2 in., 6 in.

set 3
14 mm, 13 mm, 15 mm

set 4
10 ft, 30 ft, 20 ft

set 1
set 2
set 3
set 4

The answer is set 1, this is because you can do pythagoras' theorem and say that 10^2 + 24^2 must equal 26^2, so:
100 + 576 = 676
√676 = 26
and therefore set 1 is a right angled triangle because pythagoras' theorem only works on right angled triangles
hope this !