MHT CET · Maths · Permutation Combination
The numbers can be formed using the digit \(1,2,3,4,3,2,1\) so that odd digits always occupy odd places in 
ways.
- A 9
- B 18
- C 6
- D 3
Answer & Solution
Correct Answer
(B) 18
Step-by-step Solution
Detailed explanation
We have 4 odd digits i.e. 1,1,3,3 and 3 even digits i.e. 2,2, 4 In a 7 digit number, there are 4 odd and 3 even places.
So number of possible ways \(=\frac{4 !}{2 ! 2 !} \times \frac{3 !}{2 !}=18\)
So number of possible ways \(=\frac{4 !}{2 ! 2 !} \times \frac{3 !}{2 !}=18\)
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