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how many digits are these : 0, 1, 2.... 7 ?
Okay then 7*7*6*5*4
you want a 5 digit number, how many ways u can fill first space ?
wait the .....means 0,1,2,3,4,5,6,7 right?
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...
^ No that can't be 8!
from where is 3! coming from?
^ You can't have 0 in the first place. Since, 09 or 095 is treated as 1 and 2 digits numbers repectively.
cuz its 5 spots 8*7*6*5*4
It's 5 spots so won't it be 5!?
@ganeshie8 teach your student!
Why are we subracting? :o
gotta love dan.
how many ways we can fill first space ?
do we have 120 digits ?
then ? how did u get 120 ha
5! is correct, if u have oly 5 digits
but we got more digits here... we have 8 digits to use here
You asked me about 5,okay so if 8! then 40,320.
lets go step by step, this is lil involved than that
wat u thinking @dan815 ?
For 1st space :- since u have 8 digits to pick from, u got 8 choices to fill 1st space
but since 0 in first space wont satisfy a 5 digit number. So u have oly 7 choices for 1st space.
For 2nd space :- 1 used out of 8 available, so 7 left for 2nd space.
For 3rd space :- 2 used out of 8 available, so 6 left for 3rd space
For 4th space :- 3 used out of 8 available, so ?
um 5 left?
Then 5th space :4 used out of 8th available so 4 left
exactly ! looks u nailed it lol
Lol so 5 places are covered.
yea, now multiply all ... total number of 5 digit numbers w/o repeating = 7 x 7 x 6 x 5 x 4
w/o = with out
why without repeating? :)
How many 5 digits numbers are possible from the digits 0,1,2.....7 if each digit is used only once?
it says each digit has to be used oly once
Oh okay got it. :P
plz watch i wrote a full lecture
If you go running an see my very first comment i already said that the answer is 5040....o_O
explaining concept for scenario
5040 is not correct
different scenario http://sketchtoy.com/39678817
i think u need to get this idea down first
but 184.108.40.206.3.2.1. is 5040.
Oh wait sorry!!
try again :)
You said not to repeat digits.
I know but you 7 is coming two times,You said not to repeat digits.
5880 is the answer then.
i conveyed it incorrectly it seems when i said notto repeat digits. i meant it for something else.
Oh :D Thanks btw.
http://sketchtoy.com/39678817 URI watch it
What is that?
i drew it.. help u to understand how u can think about this stuff
u can use that little circle thing below the video to control the speed, and pause when u dont understand in the middle
ok watch this too, i introduce nCr and nPr formula literally just introduce http://sketchtoy.com/39682791