Question

PLEASE HELP This question is hard but doable.

Two sides of a (non-degenerate) triangle are 11 and 17. How many possible lengths are there for the third side, if it is a positive integer?

Answer 1

By the triangle inequality, the smaller two sides' lengths must add up to a number larger than the length of the largest side. So either

$x+11>17\implies x>6$

or

$11+17=28>x$

In other words, either $x$ is not the largest side length, or it is.

Taken together, we must have $6<x<28$, which yields 22 integer solutions.

Answer 2

17 - 11 = 6
17 + 11 = 28
6 < third side <28

so any side from 7 to 27 are possible lengths

answer
there are 21 possible lengths for third side if it is a positive integer