Thursday, January 25, 2007

"GRE MATH PROBLEM OF THE DAY"

A polygon has 44 diagonals, and then number of sides are ?
A) 7
B) 8
C) 9
D) 10
E) 11
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5 comments:

Anonymous said...

why 11?

January 25, 2007 at 8:47 AM
Anonymous said...

Answer is 11. I started with 4, 5, 6 sides of polygon & just saw the pattern. But it took little bit more time than should have for test. Is there any other way to do it?

January 25, 2007 at 2:32 PM
Anonymous said...

dint get it..cud neone explain?

January 26, 2007 at 1:06 AM
snj153 said...

the pattern of no. of diagnols starting with 4 sided polygon is 2,5,,9,14,20,27,35,44...this is nothing but sum of natural no. i.e.2+3+4+5+6+7+8+9=44
4-5-6-7-8-9-10-11-----sides

simply try this formula n(n+1)/2
9(9+1)/2 = 45(nearly 44)
9+2=11 (always add 2 to n to get the ans.
u can try for others also
suppose 35 dia

January 26, 2007 at 1:22 AM
Anonymous said...

For a an n sided polygon - the number of diagonals drawm from a vertex is (n-3)
therfore if there are x diagonals , then the number of sides will be

n*(n-3)=2x

solve for n
u will gwt 2 values 11 and -8
ans=11

January 26, 2007 at 7:04 PM

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