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SSC Sample Paper Mock Test-4 SSC CGL Tear-II Paper-1

  • question_answer
    The difference between the interior and exterior angles of a regular polygon is \[60{}^\circ .\] Then, how many sides are there in that polygon?             

    A)  5                                

    B)  6   

    C)  7                                

    D)  8 

    Correct Answer: B

    Solution :

      Here, (interior angle) \[-\] (exterior angle) \[=60{}^\circ \] \[\Rightarrow \]   \[\frac{(n-2)\times 180}{n}-\frac{360}{n}=60\] \[\Rightarrow \]   \[\frac{1}{n}[(n-2)\times 180-360]=60\] \[\Rightarrow \]   \[\frac{1}{n}[180\,n-360-360]=60\] \[\Rightarrow \]   \[\frac{1}{n}[180\,n-720]=60\] \[\Rightarrow \]   \[180\,n-720=60n\] \[\Rightarrow \]   \[180\,n-60\,n=720\] \[\Rightarrow \]   \[120\,n=720\] \[\therefore \]      \[n=6\] Therefore, the polygon contains 6 sides.        


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