16Hit1600
Geometry and TrigonometryVery hardCounting possible integer third sides

Geometry and Trigonometry practice question

Two sides of a triangle have lengths 7 and 12. If the third side has an integer length, how many different lengths are possible for the third side?

Answer: 13

The third side must satisfy 12 − 7 < x < 12 + 7, so 5 < x < 19: the integers 6 through 18, which is 13 values.

Common wrong answers

If you answered 12
12 misses one end of the range.
If you answered 14
14 wrongly includes an endpoint; the inequalities are strict.
If you answered 19
19 counts every integer up to the sum.

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