I was looking into numerology and it's pretty interesting to see how your name and birthdate are broken down into numbers and the categories that are used to assign numbers to them. My breakdown is the following:
Soul # 6
Personality # 6
Power Name # 6
Birth Day # 6
Life Path # 3
Attitude # 5
Destiny # 7
My number is 6666357
• We have 7 categories
• Each category can be assigned a number between 1 - 9
• The lowest number can be 1111111
• The highest number can be 9999999
Question
How many number combination could you actually create with the rules above?
What would the odds be of someone else actually having the exact same match as the number above? I'm thinking of almost a lottery breakdown.
7 matches means 1 - 45,000,000
6 matches means 1 - 3,200,000
5 matches means 1 - 180,000
I'm not sure how I would answer this...Looking to understand how someone would solve this as I think it's an interesting math problem.
There are $9^7$ number combinations, since each of the $7$ entries can have any one of $9$ values.
Let $A$ and $B$ be any two strings of length $7$ made up of the symbols $1$ to $9$. We want the probability that $B$ matches $A$ in exactly $k$ places, where $k$ goes from $0$ to $7$. That takes care of your particular questions, and more.
In order to answer the question, we need to make some assumptions. The simplest assumption is that all $9^7$ strings are equally likely. Unfortunately, this assumption is undoubtedly grossly false.
Let us go on, with the understanding that the numbers we come up with are likely to bear very little relation to the truth.
Let $A$ be given. We count how many $B$'s match $A$ in exactly $k$ places. Which places? These can be chosen in $\binom{7}{k}$ ways. Now in the remaining $7-k$ places, $B$ must not match $A$, so for each of these places there are $8$ values that the string $B$ can take on.
It follows that there are exactly $\binom{7}{k}8^{7-k}$ ways for $B$ to match $A$ in exactly $k$ places. Thus, for the "equally likely" model, the probability that $B$ matches $A$ in exactly $k$ places is $$\frac{\binom{7}{k}8^{7-k}}{9^7}.\tag{$1$}$$
Remark: We should stress again that the "equally likely" model is a very poor one. The real probability of a moderately large number of matches, such as $4$ to $7$, is undoubtedly far higher than predicted by Formula $(1)$. If this were a question that mattered, it would be highly irresponsible to give $(1)$ as the answer.