Saturday, 25 January 2014

Question of the Day No. 21




a) 30     b) 27     c) 25     d) 28     e) 31

Answers and Explanations are welcome in comments

The Correct Answer will be Given Tomorrow
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1 comment:

  1. Unknown26 January 2014 at 21:49

    Correct Answer is 27
    Explanation : It is very complicated to count each and every triangle so note down the formula to count triangles in triangle

    1st check the number of triangles in base. The number of base triangles are either Even or Odd

    If number of base triangles are even then
    1/8{n(n+2)(2n+1)}

    If number of base triangles are odd then
    1/8{n(n+2)(2n+1)-1}

    n is number of base triangles

    so in Question No. 21 number of base triangles are 4. 4 is even number
    1/8{4*(4+2)*(2*4+1) = 1/8*24*9 = 27

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