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dear sir/madam, i am having doubt in the following question for some time now and iit is on 11th ,so please help...! "In how many ways 10 speakers can speak at a function such that A speaks before B and B speaks before C." the answer is 10!/3! i cannot understand how.Please help.

dear sir/madam, i am having doubt in the following question for some time now and iit is on 11th ,so please help...!


"In how many ways 10 speakers can speak at a function such that A speaks before B and B speaks before C."


the answer is 10!/3!


i cannot understand how.Please help.

Grade:12

2 Answers

Priyansh Goel
21 Points
12 years ago

Follow these steps:

1.  Select A,B,C from 10 people in 10C3 ways.

2.   Arrange A,B,C in only 1 way. AS Ais before B and Bis before C.

3.   All others remaining can be permuted in 7! ways.

 

So, total : 10C3 *1*7!.

Solve this to get ur answer.

 

h v
33 Points
11 years ago

thanks for the answer

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