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21 Aug 2011, 23:08
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How many triangles can be made within pentagon and this pentagon has a one point at centre too ?
Ans is : 20 , but with my approach its coming out 15.
Ans is : 20 , but with my approach its coming out 15.
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This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
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21 Aug 2011, 23:32
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The total number of possible triangles is 20.
Let N be the number of sides in a polygon.
Total number of diagonals in a polygon is given by (1/2)*N*(N-3)
Total number of triangles that can be made from one vertex along the diagonals to other vertex is given by the formula (N-2)
Applying it for pentagon. Number of diagonals is 5.
Total no. of. triangles from a vertex is 5-2 =3.
So total no. of triangles from all the 5 vertices are 5*3 =15.
And taking the point in centre into account we can make another 5 triangles.
Hence 15 + 5 = 20.
But the count 20 is not the number of distinct triangles.
Let N be the number of sides in a polygon.
Total number of diagonals in a polygon is given by (1/2)*N*(N-3)
Total number of triangles that can be made from one vertex along the diagonals to other vertex is given by the formula (N-2)
Applying it for pentagon. Number of diagonals is 5.
Total no. of. triangles from a vertex is 5-2 =3.
So total no. of triangles from all the 5 vertices are 5*3 =15.
And taking the point in centre into account we can make another 5 triangles.
Hence 15 + 5 = 20.
But the count 20 is not the number of distinct triangles.
22 Aug 2011, 03:05
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Thanks for a quick reply 
Is there any way to find out distinct triangles?
Is there any way to find out distinct triangles?
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
