uri
  • uri
How many 5 digits numbers are possible from the digits 0,1,2.....7 if each digit is used only once?
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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uri
  • uri
@terenzreignz
ganeshie8
  • ganeshie8
how many digits are these : 0, 1, 2.... 7 ?
uri
  • uri
8.

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More answers

ganeshie8
  • ganeshie8
|dw:1371472595398:dw|
anonymous
  • anonymous
Okay then 7*7*6*5*4
ganeshie8
  • ganeshie8
you want a 5 digit number, how many ways u can fill first space ?
uri
  • uri
wait the .....means 0,1,2,3,4,5,6,7 right?
ganeshie8
  • ganeshie8
yes...
anonymous
  • anonymous
See, for the first place you can choose any of the 7 digits except 0. for the second you have 7 choices and so on...
anonymous
  • anonymous
^ No that can't be 8!
dan815
  • dan815
8!/3!
uri
  • uri
8.7.6.5.4.3.2.1?
uri
  • uri
from where is 3! coming from?
anonymous
  • anonymous
^ You can't have 0 in the first place. Since, 09 or 095 is treated as 1 and 2 digits numbers repectively.
dan815
  • dan815
cuz its 5 spots 8*7*6*5*4
uri
  • uri
It's 5 spots so won't it be 5!?
dan815
  • dan815
or8!/(8-5)! =8!/3!
dan815
  • dan815
oh my
dan815
  • dan815
@ganeshie8 teach your student!
uri
  • uri
Why are we subracting? :o
anonymous
  • anonymous
gotta love dan.
ganeshie8
  • ganeshie8
|dw:1371473092868:dw|
ganeshie8
  • ganeshie8
how many ways we can fill first space ?
ganeshie8
  • ganeshie8
|dw:1371473129915:dw|
uri
  • uri
120 ways?
ganeshie8
  • ganeshie8
do we have 120 digits ?
uri
  • uri
No o_O
ganeshie8
  • ganeshie8
then ? how did u get 120 ha
uri
  • uri
5! @ganeshie8
ganeshie8
  • ganeshie8
5! is correct, if u have oly 5 digits
ganeshie8
  • ganeshie8
but we got more digits here... we have 8 digits to use here
uri
  • uri
You asked me about 5,okay so if 8! then 40,320.
ganeshie8
  • ganeshie8
lets go step by step, this is lil involved than that
anonymous
  • anonymous
wat u thinking @dan815 ?
uri
  • uri
Alright..
ganeshie8
  • ganeshie8
For 1st space :- since u have 8 digits to pick from, u got 8 choices to fill 1st space
uri
  • uri
Hmm
ganeshie8
  • ganeshie8
but since 0 in first space wont satisfy a 5 digit number. So u have oly 7 choices for 1st space.
ganeshie8
  • ganeshie8
|dw:1371473613311:dw|
ganeshie8
  • ganeshie8
For 2nd space :- 1 used out of 8 available, so 7 left for 2nd space.
ganeshie8
  • ganeshie8
|dw:1371473655724:dw|
ganeshie8
  • ganeshie8
For 3rd space :- 2 used out of 8 available, so 6 left for 3rd space
ganeshie8
  • ganeshie8
|dw:1371473687769:dw|
ganeshie8
  • ganeshie8
For 4th space :- 3 used out of 8 available, so ?
uri
  • uri
um 5 left?
ganeshie8
  • ganeshie8
Yes !
uri
  • uri
Then 5th space :4 used out of 8th available so 4 left
ganeshie8
  • ganeshie8
exactly ! looks u nailed it lol
ganeshie8
  • ganeshie8
|dw:1371473967919:dw|
uri
  • uri
Lol so 5 places are covered.
ganeshie8
  • ganeshie8
yea, now multiply all ... total number of 5 digit numbers w/o repeating = 7 x 7 x 6 x 5 x 4
ganeshie8
  • ganeshie8
w/o = with out
uri
  • uri
why without repeating? :)
ganeshie8
  • ganeshie8
How many 5 digits numbers are possible from the digits 0,1,2.....7 if each digit is used only once?
ganeshie8
  • ganeshie8
it says each digit has to be used oly once
uri
  • uri
Oh okay got it. :P
ganeshie8
  • ganeshie8
good :)
uri
  • uri
5040.
dan815
  • dan815
http://sketchtoy.com/39678817
dan815
  • dan815
plz watch i wrote a full lecture
uri
  • uri
If you go running an see my very first comment i already said that the answer is 5040....o_O
dan815
  • dan815
explaining concept for scenario
ganeshie8
  • ganeshie8
5040 is not correct
dan815
  • dan815
different scenario http://sketchtoy.com/39678817
dan815
  • dan815
i think u need to get this idea down first
uri
  • uri
but 7.6.5.4.3.2.1. is 5040.
ganeshie8
  • ganeshie8
|dw:1371474277420:dw|
uri
  • uri
Oh wait sorry!!
uri
  • uri
840.
ganeshie8
  • ganeshie8
try again :)
uri
  • uri
You said not to repeat digits.
ganeshie8
  • ganeshie8
|dw:1371474383493:dw|
uri
  • uri
I know but you 7 is coming two times,You said not to repeat digits.
uri
  • uri
5880 is the answer then.
ganeshie8
  • ganeshie8
Yes !
ganeshie8
  • ganeshie8
i conveyed it incorrectly it seems when i said notto repeat digits. i meant it for something else.
uri
  • uri
Oh :D Thanks btw.
dan815
  • dan815
http://sketchtoy.com/39678817 URI watch it
uri
  • uri
What is that?
dan815
  • dan815
i drew it.. help u to understand how u can think about this stuff
uri
  • uri
Alright. :)
dan815
  • dan815
u can use that little circle thing below the video to control the speed, and pause when u dont understand in the middle
uri
  • uri
Neat.
dan815
  • dan815
ok watch this too, i introduce nCr and nPr formula literally just introduce http://sketchtoy.com/39682791

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