Permutations and Combinations

• Fundamental Principle of Counting: If an event occurs in m different ways, following which another event occurs in n different ways, then the total number of occurrence of the events in the given order is m × n. This is called the fundamental principle of counting.

      Find the number of 5-letter words, with or without meaning, which can be formed out of the letters of the word MATHS,             where the repetition of digits is not allowed.

      Solution:
      There are as many words as there are ways of filling 5 vacant places  by the 5 letters.
      The first place can…