Misc 1 - Chapter 6 Class 11 Permutations and Combinations

Transcript

Misc 1 How many words, with or without meaning, each of 2 vowels and 3 consonants can be formed from the letters of the word DAUGHTER? Number ways of selecting 2 vowels & 3 consonants = 3C2 × 5C3 = 3!/2!(3 − 2)! × 5!/3!(5 − 3)! = 3!/2!1! × 5!/3!2! = 30 Now, Each of these 5 letters can be arranged in 5 ways Number of arrangements = 5P5 = 5!/(5 − 5)! = 5!/0! = 5! = 5 × 4 × 3 × 2 × 1 = 120 Thus, Total number of words = Number of ways of selecting × Number of arrangements = 30 × 120 = 3600