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# A restaurant is hanging 7 large tiles on its wall in a single row

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Senior Manager
Joined: 02 Jan 2017
Posts: 293
A restaurant is hanging 7 large tiles on its wall in a single row  [#permalink]

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17 Feb 2017, 16:37
2
00:00

Difficulty:

15% (low)

Question Stats:

78% (01:07) correct 22% (01:51) wrong based on 82 sessions

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A restaurant is hanging 7 large tiles on its wall in a single row. How many arrangements of tiles are possible if there are 3 white tiles and 4 blue tiles?

A. 35
B. 12
C. 21
D. 84
E. 28
Math Expert
Joined: 02 Aug 2009
Posts: 7991
Re: A restaurant is hanging 7 large tiles on its wall in a single row  [#permalink]

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17 Feb 2017, 19:40
vikasp99 wrote:
A restaurant is hanging 7 large tiles on its wall in a single row. How many arrangements of tiles are possible if there are 3 white tiles and 4 blue tiles?

A. 35
B. 12
C. 21
D. 84
E. 28

Hi..

Total ways these 7 tiles can be arranged =7!
However these contain duplicity as 3 tiles are of one colour and other 4 are of other colour..
So eliminating these = $$\frac{7!}{3!4!}$$=35

A
_________________
Senior Manager
Joined: 17 Mar 2014
Posts: 429
Re: A restaurant is hanging 7 large tiles on its wall in a single row  [#permalink]

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20 Jan 2019, 08:21
vikasp99 wrote:
A restaurant is hanging 7 large tiles on its wall in a single row. How many arrangements of tiles are possible if there are 3 white tiles and 4 blue tiles?

A. 35
B. 12
C. 21
D. 84
E. 28

Hello Bunuel,

Isn't this question confusing. 3 White tiles could be different white tiles and/or 4 blue tiles could be different blue tiles ? How we can make sure that all white/blue tiles are similar ?

Thanks,
Amm
Senior Manager
Joined: 15 Feb 2018
Posts: 367
Re: A restaurant is hanging 7 large tiles on its wall in a single row  [#permalink]

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20 Jan 2019, 17:59
ammuseeru
I understand your attention to detail (based on some convoluted and tricky gmat questions), but it I have not found it necessary for combination questions. Most people (including and especially me) find this section confusing. The questions ask straight forward questions and simply require application of rules. This question tests 'permutation with repeated elements'.

$$P(n; n_1, n_2, . . . , n_k) = \frac{n!}{n_1! n_2! . . . n_k!}$$
Re: A restaurant is hanging 7 large tiles on its wall in a single row   [#permalink] 20 Jan 2019, 17:59
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