Question

Stacy prepared 20 different letters to be sent to 20 addresses. For each letter she prepared an envelope with its correct address. If the 20 letters to be put in to 20 envelopes at random, what is the probability that exactly 19 letters will be put in to the envelope with the correct address?

Answer 1

.

Answer 2

(1/20)^19 ?

Answer 3

If 19 letters are in the correct envelopes, then the last letter must also be in the correct envelope.
The probability of all 20 envelopes in the correct order is 1/20!

Answer 4

:O

Answer 5

yes i agree!

Answer 6

total possibilties - prob of 1 wrong, and prob of 0 wrong

Answer 7

yeah that looks pretty neat, i guess then we can conclude the probability for exactly 19 letters putting in correct envelopes is 0 ?

Answer 8

oh wait lol everything is wring oops xD

Answer 9

@dan815 Could you help with this math question

Answer 10

everything is right*

Answer 11

xD

Answer 12

the probabilitly is 0!

Answer 13

oh its impossible :)

Answer 14

trying to trick us -.-

Answer 15

shame on this question

Answer 16

guess i was partially successful :P

Answer 17

lol

Answer 18

-.-

Answer 19

Hello

Answer 20

What about 19 or above

Answer 21

Could someone Help me http://openstudy.com/study#/updates/55912961e4b0428366270957

Answer 22

At least 19 correct

Answer 23

im half a sleep anyway xD

Answer 24

Then it would be 1/20!

Answer 25

You guys are so mean Please Help :(



Could someone Help me
http://openstudy.com/study#/updates/55912961e4b0428366270957

Answer 26

total permutations : 20!
permutations in favor : 1

so yeah.. 1/20!

on cursory thinking, this doesn't look like a binomial distribution, so other cases can get complicated hmm

Answer 27

try 10 to be correct ?

Answer 28

Question: you have 20 envelopes and 20 letters; 19 are correct matching. Is it not that 20 are matching?? Since 19 right, how can the rest is wrong?