prob q (1 Viewer)

[ToO LaZy ^*]

how many numbers of 7 digits can be formed from the digits 1,2,3,4,5,6,7 if there are not more than 2 digits between 1 and 2?

 

[Archman]

a lot.

2!*5!*(6+5+4), whatever that is.

 

[Rorix]

i'd say its about 1234567


give or take

 

[ToO LaZy ^*]

a lot.

2!*5!*(6+5+4), whatever that is.

could you explain that pleaseeeee
EDIIT: nevermind, figured it out.

 

[fush]

please explain to me..i still dont get it

this is my worse 3u topic

 

[Rush152]

i'm not sure if i'm completely right on this or at all.. well better than no working i guess..

(2! x 4! x 5!) + (2! x 5! x 5!) + (2! x 6! x 5!)
=207360

1st bracket is if 2 is between, 2nd bracket if 1 inbetween, 3rd if none are between

bleh? sounds kinda like what archman was doing err..
is what i've done right? lol

 

[speersy]

i dont understand why each is multiplied by 5!