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How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8

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Manager
Manager
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G
Joined: 25 Dec 2018
Posts: 148
Location: India
GMAT 1: 490 Q47 V13
GPA: 2.86
How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8  [#permalink]

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New post 20 Jan 2019, 09:14
1
3
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

88% (00:50) correct 13% (02:19) wrong based on 8 sessions

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How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8 and 9, without repetition, so that 2 and 5 are not adjacent?

A. 120
B. 180
C. 288
D. 360
E. 720
Director
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G
Joined: 09 Mar 2018
Posts: 958
Location: India
Re: How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8  [#permalink]

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New post 20 Jan 2019, 09:48
2
akurathi12 wrote:
How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8 and 9, without repetition, so that 2 and 5 are not adjacent?

A. 120
B. 180
C. 288
D. 360
E. 720


- - - -

Total 4 digits which can be found without repetition = 6*5*4*3 = 360

Automatically you can remove D and E.

Now in these - - - - dashes, if i consider the cases when 2 & 5 will be adjacent, i can just subtract it from the total
2 5 - -
- 2 5 -
- - 2 5

In each case remaining places will be filled with the remaining 4 numbers in 4 * 3 ways, Total will be 36(since 2 and 5 will take 1 position each)

Order can change as well which will result in 72 ways

4 digit numbers can be formed without repetition, so that 2 and 5 are not adjacent = 360 - 72 = 288

Answer C
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Joined: 02 Sep 2009
Posts: 52907
Re: How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8  [#permalink]

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New post 20 Jan 2019, 20:28
akurathi12 wrote:
How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8 and 9, without repetition, so that 2 and 5 are not adjacent?

A. 120
B. 180
C. 288
D. 360
E. 720


Discussed here: https://gmatclub.com/forum/how-many-4-d ... 66550.html
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Re: How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8   [#permalink] 20 Jan 2019, 20:28
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How many 4 digit numbers can be formed using the digits 1, 2, 5, 6, 8

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