Two signs of a triangle are 10 mm and 7 mm. Determine the length of the third side from the choices given.
2 mm
20 mm
1 mm
5 mm
The third side of a triangle must be greater than the difference of the other two sides and less than the sum of the other two sides.
In this case, the third side must be greater than |10 - 7| = 3 mm and less than 10 + 7 = 17 mm.
Therefore, the correct answer is 5 mm.