Math CentralQuandaries & Queries


Question from Judy:

I wrote previously and need more help. I need to generate a list of 4 digit. Numbers using 0-9 with no repetitions
I know that there is a 6 followed by a 2. Order does matter
Thank you in advance for your help.

Hi Judy,

Since there is a 6 followed by a 2 there are 3 possible patterns for your 4 digit strings.


where x and y are digits from 0, 1, 3, 4, 5, 7, 8, 9 with $x \neq y.$ For each of he 3 patterns you have 8 choices for $x,$ and once $x$ is chosen there are 7 possible choices for $y.$ Hence each of the 3 possible patterns gives $8 \times 7,$ 4 digit strings. Thus in total you have $3 \times 8 \times 7,$ 4 digit strings.

I hope this helps,

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