Question

Which set of numbers cannot represent the lengths of the sides of a triangle A) 7,9,12 B) 8,6,7 C) 8,20,12 D) 10,13,20

Answer 1

Hi Friend

You should make use of the Triangle Inequality Theorem, which states that

the sum of the lengths of two sides of a triangle must always be greater than the length of the third side

As you test the answers, you will notice that in C 7+11=18, which is also equal to the length of the other side. This is impossible so the answer is C.