Question

Permutation question: please find it in the picture below:

Answer 1

b) 8P20 = 6720

Answer 2

Please explain... :(

Answer 3

shouldnt it be \[\frac{8!}{(8-5)!}\]

Answer 4

you have 8 distinct alphabets..you'll form 5 letter words

Answer 5

therefore you get \[\frac{8!}{(8-5)!} = \frac{8!}{3!}\]

Answer 6

8P20 = 8!/(8-5)!

Answer 7

^not 20, 5

Answer 8

that's also equal to \[\frac{8 \times 5 \times 4 \times \cancel{3!}}{\cancel{3!}} = 8 \times 7 \times 6 \times 5 \times 4 = 6720\]

Answer 9

that'show it was got

Answer 10

If i have the 8 letters {a,b,c,d,e,f,g,h}
and pick 5 of them,
I could start with any of them, so I have 8 ways of doing this.
Next, I have 7 letters left, so I have 7 ways of doing this.
Then I have 6,
Then 5.
Then 4. End

So 8*7*6*5*4 = 6720

let n = total number of letters
let r = total chosen

Formula to get answer is nPr (its on your calculator)
But expanded, its simply:

n!
______
(n-r)!