Seven friends (Sally, Jean, Ruth, Emma, Amir, Claude and Abdu) are about to sing

Question

Seven friends (Sally, Jean, Ruth, Emma, Amir, Claude and Abdu) are about to sing-file down a narrow path. a) With respect to the order of the individuals as they walk down the path, how many different permutations are there? b)How many different permutations are there if Sally and Emma refuse to take the lead and Amir must be in the rear?

a) With respect to the order of the individuals as they walk down the path, how many different permutations are there?

b) How many different permutations are there if Sally and Emma refuse to take the lead and Amir must be in the rear?

Explanation / Answer

a) Number of different permutations = 7! = 5040

b) Here for lead place, we have only 4 choices since Sally and Emma won't be there and Amir will be the last. Also, the last place is fixed so we need to arrange a total of 6 persons.

So,

Number of different permutations = 4*5*4*3*2*1*1 = 480

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.