Krishna
0

Step 1: First, understand the concept of permutations and

         combinations

  Link: https://medium.com/i-math/combinations-permutations-fa7ac680f0ac


Step 2: Note down the main points given.

              Given number  223355888

            We have to rearrange the digits  

                 (odd digits occupy even positions)

            

Step 3: Find out odd and even places

           223355888

        There are 4 even places and 5 odd places.


Step 4: Find out the possible ways

  Odd numbers 3355 are placed in these 4 places in = \frac{4!}{2!.2!} ways


Even digits are 22888.

These even digits are placed in 5 odd places in = \frac{5!}{3!.2!} ways


Step 5: Find the total number of ways  

∴ No. of required 9 digit numbers=  \frac{4!}{2!.2!} * \frac{5!}{3!.2!}

                                                   = \frac{4*3*2*1}{2*2} \frac{5*4*3*2*1}{3*2*2*1}

                                                  = 6 * 10

                                                  = 60