Question

A triangle has side lengths 21 and 17. Which is a possible length for the third side?

Answer 1

the difference between two sides of a triangle must be small than the third side.

Answer 2

25 or 13

Answer 3

third side must be less than 28

Answer 4

must be greater than 14 but less than 28

Answer 5

third side must be between 38 and 4
because we already know that the side lengths 21 and 17
21 – 17 = 4
and
21 + 17 = 38

The triangle inequality theorem states that any side of a triangle is always shorter than the sum of the other two sides.
http://www.mathopenref.com/triangleinequality.html

Answer 6

digest the definition of triangle inequality theorem