Permutations and Combinations (1 Viewer)

[Dreamerish*~]

1. How many numbers greater than 4000 can be formed with the figures 3, 5, 7, 8, 9? (Repetition not allowed)

2. In how many ways can 5 boys and 3 women be arranged in a row?

Thanks guys.

 

[withoutaface]

1. ok, the first digit must be 5, 7, 8, or 9, since it must be >4000. Hence there are 4 possible combs for the first digit. The second digit has no such restriction, and hence it can have any of the 4 left, and so on. Hence 4*4*3*2*1= 16*6 = 96

2. 8! It doesnt matter that they're men and women, and we'd have to assume that they're distinct human beings.

 

[Dreamerish*~]

1. ok, the first digit must be 5, 7, 8, or 9, since it must be >4000. Hence there are 4 possible combs for the first digit. The second digit has no such restriction, and hence it can have any of the 4 left, and so on. Hence 4*4*3*2*1= 16*6 = 96

2. 8! It doesnt matter that they're men and women, and we'd have to assume that they're distinct human beings.

Yeah! That's exactly right.

Except the textbook has 240 for the first question.

For the second, as if it wasn't enough that they accidentally switched the answers of a) and b) around, they calculated the number of arrangements according to the fact that the boys are always standing together and likewise for women. A fact which was not given in the question.

Fitzpatrick textbooks should be burnt.

 

[Slidey]

Fitzpatrick is actually pretty good with questions, Dreamerish.

 

[Dreamerish*~]

Fitzpatrick is actually pretty good with questions, Dreamerish.

Oh, their questions are good. :uhhuh:

They make a lot of mistakes in their answers though. It can be really frustrating.

 

[yook]

doesnt that suck..
i borrowed fitzpatrick to prac 3u stuff before tommorow.. now im turned off by it..

btw like ure dp, dreamerish.. i love house [she is from house right???!]

 

[Dreamerish*~]

doesnt that suck..
i borrowed fitzpatrick to prac 3u stuff before tommorow.. now im turned off by it..

btw like ure dp, dreamerish.. i love house [she is from house right???!]

Thanks, yeah she is.

<3 Cameron.

 

[thunderdax]

I hate to say this, but waf is wrong with question 1. The question doesn't specify only 4 digit numbers so the answer is
perms=4*4*3*2+5!=216.

But that still isn't what the textbook says so I guess I'm wrong too...

 

[withoutaface]

Fuck, I forgot there were 5 digits and not 4.

 

[wanton-wonton]

I hate to say this, but waf is wrong with question 1. The question doesn't specify only 4 digit numbers so the answer is
perms=4*4*3*2+5!=216.

But that still isn't what the textbook says so I guess I'm wrong too...

I think you're right. 2*5! = 240, which is not right.