Question

In a group of 8 girls, two girls are sisters. The number of ways in which the girls can sit so that two sisters are not sitting together is

Solution

Correct option is

None of these

The required number of ways

     = the number of ways in which 8 girls can sit – the number of  ways in which two sisters are together     

     = 8! – (2) (7!) = 30240.

SIMILAR QUESTIONS

Q1

If 0 < r < s ≤ n and nPr = nPs, then value of r + s is

Q2

, then value of is

Q3

 is maximum where m is   

 

Q4

An eight digit number divisible by 9 is to be formed by using 8 digits out of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 without replacement. The number of ways I which this can be done is  

Q5

The number of rational numbers lying in the interval (2008, 2009) all whose digits after the decimal point are non-zero and are in deceasing order is

Q6

The number of positive integral solutions of the equation  is

Q7

The exponent of 7 in 100C50 is

Q8

In the certain test there are n questions. In this test 2k students gave wrong answers to at least (n – k) questions, where k = 0, 1, 2, …, n. If the total number of wrong answer is 4095, then value of n is 

Q9

If n > 1 and n divides (n – 1)! + 1, then 

Q10

The number of words that can be formed by using the letters of the word MATHEMATICS that start as well as end with T is