Question

If a triangle has sides that are 21 and 6 what is the range for third side x?

Enter your answer without spaces in range format.
Example: 1<x<3​

Answer 1

15<x<27

Explanation:

Rule for the sides of a triangle:

The sum of the two smallest sides of a triangle must be greater than the biggest side.

In this question:

Sides of 6, 21 and x. We have to find the range for x.

If 21 is the largest side:

Two smallest are 6 and x.

x + 6 > 21

x > 21 - 6

x > 15

If x is the largest side:

Two smallest and 6 and 21. So

21 + 6 > x

27 > x

x < 27

Then

x has to be greater than 15 and smaller than 27. So the answer is:

15<x<27