Question

Which three side length CANNOT be used to form a triangle

A. 9,9,9
B. 9,9,10
C. 9,12,15
D. 9,12,25​

Answer 1

Answer: D. 9,12,25​

Explanation:

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

✓ A. 9,9,9

9 + 9 = 18, 18 > 9

✓ B. 9,9,10

9 + 9 = 19, 18 > 10 10 + 9 = 19, 19 > 9

✓ C. 9,12,15

9 + 12 = 21, 21 > 15 15 + 12 = 27, 27 > 9 9 + 15 = 24, 24 > 12

✗ D. 9,12,25​

9 + 12 = 21, 21 < 25, these sides cannot be used to form a triangle.