Is the triangle depicted above isosceles? (Figure not necessarily drawn to scale.)
According to the OG an isosceles triangle has at least
two sides of the same length.
a + b + c =180°
(1) 180° − (a + c) = 60° --> a + c =120° --> b = 60°. Now, if a = b = c = 60°, then the triangle is isosceles (equilateral) but if a = 100°, b = 60° and c = 20°, then the triangle is NOT isosceles. Not sufficient.
(2) a = 2b − c --> a + c =2b --> 2b + b = 180° --> b = 60°. The same as above. Not sufficient.
(1)+(2) Both statements provide with the same infor. Not sufficient.
Notice that if we define an isosceles triangle as a triangle with exactly
two equal sides (not the case for the GMAT
) then the answer will be D.
Why would the answer be D in that case Bunuel? None of the statements would be able to tell us the exact values for C or A. we would just know their sum to be 180....please point out the problem in my assumptions....