16Hit1600
Geometry and TrigonometryVery hardTriangle inequality applied

Geometry and Trigonometry practice question

Which of the following could be the lengths of the three sides of a triangle?

  1. A. 4, 7, 10Correct
  2. B. 2, 3, 5
  3. C. 1, 4, 6
  4. D. 5, 5, 11

Answer: A. 4, 7, 10

Each pair of sides must sum to more than the third: 4 + 7 = 11 > 10 ✓ (and the other pairs clearly work).

Why the other answers are wrong

B. 2, 3, 5
2 + 3 = 5, which equals the third side; the triangle would be flat.
C. 1, 4, 6
1 + 4 = 5 < 6.
D. 5, 5, 11
5 + 5 = 10 < 11.

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