Skywalker wrote:Hi,

I am able to solve the following sum using either of the 2 options provided & thus feel that the answer ought to be D, but it isnt. the OA [spoiler]= A[/spoiler]. Why ?

Also. am I correct is stating that " the external angle in a triangle is = sum of the 2 opposite internal angles" is the property used while solving for 1st statement ?

u have to use the above said property.
So the left triangle will also be isosceles and hence AD=BD

Skywalker wrote:Hi,

I am able to solve the following sum using either of the 2 options provided & thus feel that the answer ought to be D, but it isnt. the OA [spoiler]= A[/spoiler]. Why ?

Also. am I correct is stating that " the external angle in a triangle is = sum of the 2 opposite internal angles" is the property used while solving for 1st statement ?

you are having the same problem as i am having... lol... its just because we dont pay attention or dont focus on the maths...
statement 2 will be sufficient if we know the length of some side, however we dont know anything about the length of any side....thus although we know that BD=AD=BC but we have no length thus no answer
the correct answer is A