how many computer passwords with 5 characters can be formed with the letters T,U,R,N,K,E,Y?

Question

if repetitions are not allowed

Answer 1

it's a permutation with 5 letters picked up among 7 letters
Permutation is the rearrangement of objects or symbols into distinguishable sequences.

so it's 7P5 = ( 7! ) / ( (7-5)! ) = 5040 / 2 = 2520
the right notation would be :
.....7
..P
.....5
http://en.wikipedia.org/wiki/Permutation

by the way, I don't how many of these passwords would have a meaning

;;;;

Answer 2

The 7 letters, 7 x 6 x 5 x 4 x 3 x 2 x 1

and the 5 letter passwords means you only do the first 5 numbers in the sequence of 7!

7 x 6 x 5 x 4 x 3.

Answer: There can be 2520 different 5 letter passwords thought out with 7 different letters.

(Explained by a 13 year old)

Answer 3

Two step process: first, figure out how many ways to choose 5 from a set of 7. This is commonly worded "7 choose 5", and it equals 7!/(5!2!), which is 7*6/2 = 21

Then how many ways can you arrange those five chosen symbols? This is 5! = 120

So there are 21 times 120 possibilities, or 2520 of them

Answer 4

7!=5040

!=7*6*5*4*3*2*1

Therefore this gives you all of the possible combinations of a seven letter code with the specific seven letters allowed in any order, but as your question asks only five so 7!/(7-5)! Glad to help! your answer is 2520

Answer 5

7 * 6 * 5 * 4 * 3 = 2520
Example: (2-no. combination of 4-no. choices of 1, 2 , 3 and 4
Answer is 4 * 3 or 12
Proof of possible 2-no. combinations:
(1) 1 & 2, (2) 2 & 1, (3) 1 & 3, (4) 3 & 1, (5) 1 & 4, (6) 4 & 1, (7) 2 & 3, (8) 3 & 2, (9) 2 & 4, (10) 4 & 2, (11) 3 & 4, (12) 4 & 3

Answer 6

7 ways to choose the 1st letter
6 ways to chose 2nd
5 ways to choose 3rd
4 ways to choose 4th
3 ways to choose 3rd

so you gots 7*6*5*4*3 = 2520 passwords

a simple formula is 7! / (7-5)!

Answer 7

343

Answer 8

7P5 = 7!/(7-5)! = 2520