Geometry math question

Question

Which set of numbers could be the lengths of the sides of a triangle.

A)3,6,9

B)5,5,11

C)12,13,20

D)6,7,13

Answer 1

Pick any side. The length has to be shorter than the sum of the other two. This has to be true for all 3 sides.

 

A. 3,6,9

 

3: 6 + 9 = 15

3 < 15

 

6: 3 + 9 = 12

6 < 12

 

9: 3 + 6 = 9

9 = 9

 

A cannot be a triangle.

 

Keep going!

Answer 2

Only C ... the sum of the lengths of any 2 sides of a triangle must be greater than the length of the 3rd side.