Question

Which of the following triangles are impossible to draw? Choose all that apply.

Answer 1

These triangles are impossible:

a triangle with sides of 3 inches, 4 inches, and 8 inches
(the longest side is greater than the sum of the other 2 sides)

an obtuse equilateral triangle
(all angles in an equilateral triangle are acute)


a triangle with two right angles
The angles of ALL triangles must sum exactly to 180 degrees.  Two right angles sum to 180 degrees so the third angle would have to be zero degrees.

Answer 2

A triangle with angles of 30, 45, and 115 cannot be drawn. The interior angles of a triangle have to add up to 180, and 30+45+115=190.
A triangle with two right angles cannot be drawn because the sum of the interior angle must be 180, and 90+90 is already 180, and we still need a third angle.
A triangle with sides of 3 in, 4 in, and 8 in cannot be drawn because the sum of two sides in a triangle must be greater than the third. 3+4=7 and 7<8