During recent session in Intro slide I put my entire phone number except last three digits. It is stupid to do that.. may be or may be not..
Phone number is a 10 digit number with each digit ranging from 0-9. For example if my phone number is 3021067894 then
- Each position of phone number can vary from 0-9
- And every position is independent of other position. Example 3 at first position is not dependent upon 0 at second position.
Now coming to solve “Guessing Phone Number Problem”, for each position, from total 10 numbers only 1 can be selected. So probability of selecting a number from total ten number is 1/10. And since each position is independent of every other position we have (1/10)*(1/10)…
As I revealed 7 digits of my 10 digit phone number only 3 positions have to be guessed, simple right??
Total number of combinations: (10)*(10)*(10) = 1000 and
In that only 1 number is correct = 1.
So, likely chances of getting correct number (IN FIRST TRY) is 1/1000 = 0.001 or conversely 1-0.001 = .999.
That implies 99.9% times people still will not be able to find my number .
Me being stupid:
Assumption here is only 1 try what if someone writes a loop and puts all numbers together, then probability he has my number is 1 (Certain).
May be it not that stupid after all…
- I am not a celebrity for people to search for my number spending their valuable time
- Even if they write a loop to get my correct numbers, what is feedback mechanism to check if they have right number or if I have given first 7 digits right . May be call all numbers or may be use Machine Learning to guess my numbers…
Until next guess….