What is the sum of any n-1 angles in a n side (convex)

Question

What is the sum of any n-1 angles in a n side (convex) polygon?
1) n=5 
2) When one vertice is connected to all other vertices with lines, identical isocecle tirangles are formed with bases opposite to that one vertice.

gmat2me2 · Answer

The sum of internal angles of a "n" sided polygon is given by (2n-4)*90 From A we can get from the above formula since we know n=5 From B also we can get but I am not sure how to prove it :roll:

My pick would be D for this question

HIMALAYA · Answer

D. it is possible only with pentagon.

HongHu · Answer

Huh? What did I miss?
It didn't say it is a regular polygon did it? So for 1) the angel that's left could be any size and we are not going to know what is the sum of the other angels. For 2) we know that it is a regular polygon but without knowing how many sides there are we still can't know how big each angel is. I'd say (C).

HIMALAYA · Answer

honghu,

when "when one vertice is connected to all other vertices with lines, identical isocecle tirangles are formed with bases opposite to that one vertice" is given, is ot it sufficient to say the the polygon is regular?

pls explain...........

HongHu · Answer

Yes as I said in my post 2) does make it a regular polygon. But we don't know it for 1). 
So 
1) don't know if regular, insufficient
2) don't know number of sides, insufficient.

sparky · Answer

I said one not any

(sorry if it is confusing, I meant only one out of n)

HongHu · Answer

Oh if that is the case, it would be E then. :hmmm:

sparky · Answer

E. it is, angles of thriangles can vary, so each angle cannot be identified and so the sum of n-1 angles, only their total sum.

What is the sum of any n-1 angles in a n side (convex)

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