Q1) In a conference 10 speakers are present. If S1 wants to speak before S2 & S2 wants to speak after S3, then number of ways all the 10 speakers can give their speeches with the above restriction if the remaining 7 speakers have no objection to speak at any number is?
Q2) Passengers are to travel by a double decked bus which can accommodate 13 in the upper deck and 7 in the lower deck. The number of ways that they can be divided if 5 refuse to sit in the upper deck and 8 refuse to sit in the lower deck.
What I have done is:-
A1) S1S3S2||||||||
S3S1S2 ||||||||
Now we can arrange them acc. to :-
10C3 *2! * 10C7 * 7!
but the answer is 10!/3.
A2) 13C8* 8!* 7C5 * 5!
but the answer is 21.
please help
Q2) Passengers are to travel by a double decked bus which can accommodate 13 in the upper deck and 7 in the lower deck. The number of ways that they can be divided if 5 refuse to sit in the upper deck and 8 refuse to sit in the lower deck.
What I have done is:-
A1) S1S3S2||||||||
S3S1S2 ||||||||
Now we can arrange them acc. to :-
10C3 *2! * 10C7 * 7!
but the answer is 10!/3.
A2) 13C8* 8!* 7C5 * 5!
but the answer is 21.
please help