Question

In how many ways can two letters be selected from the english alphabet if repetition is allowed?

Answer 1

Answer:

For the letter course of action A???????B, where no letter is rehashed there are an aggregate of

24×23×22×21×20×19×18=1744364160 mixes.

Accepting An and B are fixed.

(Note: this answer accept strings of 9 letters. For an answer that expect reordering the whole letters in order in explicit 26-letter strings, see Aravind Gautam's answer, which is additionally right.)

We can name every one of the permutable situations as follows:

1 - 2 - 3 - 4 - 5 - 6 - 7

and afterward appoint opportunities for each position:

24 (all letters aside from An and B)- - 23 (all with the exception of A, B, and 1)- - 22 (all with the exception of A, B, 1, and 2)- - 21- - 20- - 19- - 18

1 - 2 - 3 - 4 - 5 - 6 - 7

24- - 23- - 22- - 21- - 20- - 19- - 18

A similar procedure can be all the more effortlessly followed along these lines:

For each letter in the first position (24), there can be 23 letters in the second position - that is 552 blends for the initial 2 positions (24*23). For each initial 2 situations there can be 22 letters in the third position - that is 552*22=12144. In the event that we proceed with this grouping, we get 12144*21*20*19*18=1744364160

This can likewise be spoken to utilizing factorials:

24!/(every minute of every day)!

That is a great deal of blends for sure! What number of them are genuine English words is an altogether extraordinary inquiry, obviously.