Permutation and combination
falcon handsome moderators
17/04/2017 at 11:28
FA KAKALOTS 09/02/2018 at 21:43
Arrcoding to the context, 4 balls must be put into 4 different tubes that each tube must have a ball. So the free balls are: 7−4=3(balls)
There are: 6.3=18(ways)
divided by 1 free ball/tube.
There are: 4.3.3=36(ways)
divided by 2 free ball/tube.
There are: 4.1=4(ways)
divided by 3 free ball/tube.
There are total: 18+36+4=58(ways)
ANSWER: 58 ways

Arrcoding to the context, 4 balls must be put into 4 different tubes that each tube must have a ball. So the free balls are: \(74=3\left(balls\right)\)
There are: \(6.3=18\left(ways\right)\) divided by 1 free ball/tube.
There are: \(4.3.3=36\left(ways\right)\) divided by 2 free ball/tube.
There are: \(4.1=4\left(ways\right)\)divided by 3 free ball/tube.
There are total: \(18+36+4=58\left(ways\right)\)
ANSWER: 58 ways
falcon handsome moderators
17/04/2017 at 11:31falcon handsome moderators
17/04/2017 at 11:29
FA KAKALOTS 09/02/2018 at 21:44
The number of ways to put 4 letters into 5 letter boxes is :
P45=5!(5−4)!=120

The number of ways to put 4 letters into 5 letter boxes is :
\(P^4_5=\dfrac{5!}{\left(54\right)!}=120\)
taylor swift
31/03/2017 at 20:43taylor swift
31/03/2017 at 20:33taylor swift
31/03/2017 at 20:30
There are : (200  1) : 1 + 1 = 200 numbers from 1 to 200
We have a sequence of twodigit numbers are as follows :
2 ; 12 ; 22 ; 32 ; ....... ; 192
Apply a formula to count numbers , we have :
(192  2) : 10 + 1 = 20
There are also numbers with 2 digits such as
20 ; 21 ; 23 ; 24 ; .... ; 29 ; 120 ; 121 ; 122 ; 123 ; ...... 129
And there are have 18 also numbers .
So , from these information , we have 38 numbers have digit 2
We have :
200  38 = 162 (numbers)
There are 162 numbers from 1 to 200 do not have the digit 2

Kokone 04/04/2017 at 14:18
There are : (200  1) : 1 + 1 = 200 numbers from 1 to 200
We have a sequence of twodigit numbers are as follows :
2 ; 12 ; 22 ; 32 ; ....... ; 192
Apply a formula to count numbers , we have :
(192  2) : 10 + 1 = 20
There are also numbers with 2 digits such as
20 ; 21 ; 23 ; 24 ; .... ; 29 ; 120 ; 121 ; 122 ; 123 ; ...... 129
And there are have 18 also numbers .
So , from these information , we have 38 numbers have digit 2
We have :
200  38 = 162 (numbers)
There are 162 numbers from 1 to 200 do not have the digit 2

Nguyen Van Hung 27/06/2017 at 20:34
There are : (200  1) : 1 + 1 = 200 numbers from 1 to 200
We have a sequence of twodigit numbers are as follows :
2 ; 12 ; 22 ; 32 ; ....... ; 192
Apply a formula to count numbers , we have :
(192  2) : 10 + 1 = 20
There are also numbers with 2 digits such as
20 ; 21 ; 23 ; 24 ; .... ; 29 ; 120 ; 121 ; 122 ; 123 ; ...... 129
And there are have 18 also numbers .
So , from these information , we have 38 numbers have digit 2
We have :
200  38 = 162 (numbers)
There are 162 numbers from 1 to 200 do not have the digit 2 .
falcon handsome moderators
31/03/2017 at 17:35
a) There are :7 x 7 x 6 x 5 = 1470 numbers
b) There are :4 x 4 x 3 x 2 = 96 even numbers

FA KAKALOTS 09/02/2018 at 21:45
a) There are :7 x 7 x 6 x 5 = 1470 numbers
b) There are :4 x 4 x 3 x 2 = 96 even numbers

Kokone 04/04/2017 at 14:18
a) There are :7 x 7 x 6 x 5 = 1470 numbers
b) There are :4 x 4 x 3 x 2 = 96 even numbers
falcon handsome moderators
31/03/2017 at 17:14
a) There are : 7 x 7 x 6 x 5 = 1470 numbers
b) There are : 4 x 3 x 2 x 1 = 24 old numbers

FA KAKALOTS 09/02/2018 at 21:45
ANSWER :
a,There are : 7 x 7 x 6 x 5 = 1470 ( numbers )
b,There are : 4 x 3 x 2 x 1 = 24 ( old numbers )
[hiu] Easy,right ?

Cố Lên Nào Các Bạn 08/04/2017 at 10:53
ANSWER :
a,There are : 7 x 7 x 6 x 5 = 1470 ( numbers )
b,There are : 4 x 3 x 2 x 1 = 24 ( old numbers )
Easy,right ?