The Triangle Inequality Theorem states that for any three lengths \( a \), \( b \), and \( c \) to form a triangle, the following conditions must be satisfied:
- \( a + b > c \)
- \( a + c > b \)
- \( b + c > a \)
Let's check each set of side lengths:
-
10, 20, 15
- \( 10 + 20 = 30 > 15 \) (True)
- \( 10 + 15 = 25 > 20 \) (True)
- \( 20 + 15 = 35 > 10 \) (True)
- These can form a triangle.
-
8, 8, 20
- \( 8 + 8 = 16 \not> 20 \) (False)
- These cannot form a triangle.
-
8, 4, 12
- \( 8 + 4 = 12 \not> 12 \) (False)
- These cannot form a triangle.
-
20, 10, 30
- \( 20 + 10 = 30 \not> 30 \) (False)
- These cannot form a triangle.
Based on the evaluations, the only set of lengths that can form a triangle is 10, 20, 15.