Let’s count – The basic principles of combinatorics, 1

Do your best in trying to solve the following problems. It is normal that this step will take some time, we recommend to perseverate and wait before looking at the complete solution of the exercises in the video or in the pdf below.

Exercise 1.

How many four letter words can be formed with an alphabet of 26 letters? How many of these are without a repeated letter?

Exercise 2.

How many three letter words without repetition of letters can be made by using the letters (a,b,c,d,e,f) in such a way that either the letter (e) or the letter (f) or both appear?