Im trying to work out a probability

Question

Im trying to work out a probability. There are 5 letters ( in the order of JGMTK), which has a factorial of 120. I made this by random on my kebord. Now, there are 78 different letters/numbers I could have choose from. whats the liklihood of me choosing those five letters in that order (JGMTK)?

Answer 1

Hi Ryan,

 

If you're allowing yourself to choose the same symbol twice, then the probability of each symbol is always 1/78, and for the specific combination of 5 is

= (1/78)^5.

 

If you are not allowing repeated symbols, then the probabilities increase after each keystroke,

= 1/78 * 1/77 * 1/76 * 1/75 * 1/74

 

In both cases, it's a very small chance.