Geometry Review

Question

Which set of numbers cannot represent the lengths of the sides of a triangle?

a.10,13,20

b.10,12,10

c.7,9,12

d.8,19,11

Explain your thinking.

Answer 1

d. 8,19 and 11

11+8 = 19

the longest side of a triangle must be less than the sum of the other 2 sides

L< A + B

19 is not less than 11+8.

when they're equal, the "triangle" degenerates and collapses into a line. You could call it a "triangle" with angles 0, 0 and 180. But it's not a real triangle.