Question 20 and 21, Exercise 6.2
Solutions of Question 20 and 21 of Exercise 6.2 of Unit 06: Permutation and Combination. This is unit of Model Textbook of Mathematics for Class XI published by National Book Foundation (NBF) as Federal Textbook Board, Islamabad, Pakistan.
Question 20
Find the number of ways that $6$ men and $6$ women seated at aaround table such that they occupy alternate seats?
Solution.
If we start fixing one woman then remaining women can occupy seats in $5!$ possible arrangements
and $6$ men may be adjusted between in $6!$ possible arrangements
and hence total possible seating arrangements $=5! \times 6!=86400$
Question 21
Make all the permutations of the following words:
WHY, SAD, TWO, MADE
Solution.
Number of words $= n = 4$
Number ot permuations of 4 things taking 4 at a time $= {}^4P_4 = 24.$ 
Go to