Total no. of ways 10 students can be arrange= 10!

total no. of ways in which all the 3 girls sit together =8!*7!

total no. of ways in which exactly 2 girls sits together =there will be two scenario: a)two girls sits together but not on extreme two seats.(i.e starting 2 seats or ending two seats from seats 1 to 10)

b) two girls sits on extreme seats(i.e either starting 2 or ending 2)

So, a)=3C2*2!*6C1*7!.

b)=2(3C2*2!*7C1*7!)

So, the answer is=10!-(8!*7!)-(3C2*2!*6C1*7!)-2(3C2*2!*7C1*7!).

plz confirm whether this sol is correct or not...

M.A Economics

Delhi School of Economics

2013-15

Email Id:sumit.sharmagi@gmail.com