think_twice's blog

By think_twice, history, 8 years ago, In English

Problem why is this solution failing?

like if i have 4 numbers -

1 2 3 4

for the composite number(except 1) that is 4 , i have 3 choices(placing 4 at 1or2or3 position) and i can arrange the 3 prime numbers in fact(3) ways so i get answer 6*3 = 18 ways but this logic fails for 5 , can someone explain the fault in logic?i am weak in combinatorics so please help me find my fault.

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