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**Hannibal lecter****Member**- Registered: 2016-02-11
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Hi, how many permutation the set has X= ={1,1,2,2,6}

int repetitions and without repetitions

Wisdom is a tree which grows in the heart and fruits on the tongue

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,386

hi Hannibal lecter

If repetitions are allowed:

If the five numbers were all different it would be 5! = 5x4x3x2x1.

But we have repeated 1s. You couldn't tell the difference between 16122 and 16122 where I have swapped the 1s around. So very possibility gets counted twice because of the repeated 1s and similarly the 2s. S we need to calculate 5! ÷ 2 ÷ 2

If repetitions are not allowed the set is effectively reduced to {1,2,6} so it's just 3! = 3x2x1.

126, 162, 261, 216, 612, 621.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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