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If you have sticks of length 1, 2, 3, 4, 5, 6, 7, 8 and 9 cm. How many different triangles con you make using 3 sticks?

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If you have sticks which measure 1, 2, 3, 4, 5, 6, 7, 8 and 9 cm (one of each). How many different triangles can you make using three of the sticks?

posted Sep 6, 2017 by anonymous

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2 Answers

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answer:
34 is the answer

answer Sep 20, 2017 by Mogadala Ramana
Please explain the answer
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Yes there are two formulas.
One is for when there are an even numbers of sticks and
the other is for when there are an odd number of sticks.

If you have sticks of lengths 1,2,3,...,n inches

The formula for when n is even is n(n-2)(2n-5)/24

The formula for when n is odd is (n-1)(n-3)(2n-1)/24

The case above is when there are 9 sticks. Since 9 is odd,
we use the formula, (n-1)(n-3)(2n-1)/24
(n-1)(n-3)(2n-1)/24 = (9-1)*(9-3)*((2*9)-1) /24
=(8*6*17)/24
=34

answer Nov 2, 2017 by Mogadala Ramana



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