twenty two slips of paper are each marked with a different letter of the alphabet and placed in a basket a slip is pulled out its letter recorded and the slip is replaced this is done 4 times find the probability that a word with no repeptition of letters is formed

Question

anonymous · Answer

did you get the last one?

anonymous · Answer

ya i did. i need help with this one!

anonymous · Answer

the last one was much harder

anonymous · Answer

Help me with this one

anonymous · Answer

they have to be all different, so it is going to be 
$$\frac{20\times 19\times 18\times 17}{20^4}$$

anonymous · Answer

that is a mistake, there are 22 letters, not 20!

anonymous · Answer

$$\frac{22\times 21\times 20\times 19}{21^4}$$

anonymous · Answer

thanks

anonymous · Answer

Hmmmmmmm... not sure I believe...