Question 1141737
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The Euler's formula is


    F - E + V = 2


    (faces - edges + vertices = 2).


Substitute  F = 11, E = 10 + 10 = 20 into the formula


    11 - 20 + V = 2,


and you will get


    V = 2 - 11 + 20 = 11 vertices.      <U>ANSWER</U>
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