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fskilnik
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The image shows an office key holder where 8 different keys must be p 04 Feb 2019, 15:04
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Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

25% (medium)

Question Stats:

76% (01:34) correct 24% (01:30) wrong based on 59 sessions

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GMATH practice question (Quant Class 18)

The image shows an office key holder where 8 different keys must be placed (one key per square).
If the two main keys must be placed in the blue squares, in how many ways can all the keys be placed in the key holder?

(A) 360
(B) 720
(C) 1440
(D) 2880
(E) 4320

Source: https://gmath.net

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C
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chetan2u
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The image shows an office key holder where 8 different keys must be p 04 Feb 2019, 19:29
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fskilnik


GMATH practice question (Quant Class 18)

The image shows an office key holder where 8 different keys must be placed (one key per square).
If the two main keys must be placed in the blue squares, in how many ways can all the keys be placed in the key holder?

(A) 360
(B) 720
(C) 1440
(D) 2880
(E) 4320

Source: https://gmath.net
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So the 8 keys are - 2 main and 6 others..
2main can be placed in 2! Ways
6 others can be placed in 6! ways

Total 2!*6!=2*720=1440

C
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The image shows an office key holder where 8 different keys must be p 05 Feb 2019, 03:47
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2 main keys can be placed in 2! ways and 6 keys in 6! ways
so total
6!*2! = 1440
IMO C


fskilnik


GMATH practice question (Quant Class 18)

The image shows an office key holder where 8 different keys must be placed (one key per square).
If the two main keys must be placed in the blue squares, in how many ways can all the keys be placed in the key holder?

(A) 360
(B) 720
(C) 1440
(D) 2880
(E) 4320

Source: https://gmath.net

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04-Feb19-12u.gif
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fskilnik
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The image shows an office key holder where 8 different keys must be p 05 Feb 2019, 06:30
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fskilnik


GMATH practice question (Quant Class 18)

The image shows an office key holder where 8 different keys must be placed (one key per square).
If the two main keys must be placed in the blue squares, in how many ways can all the keys be placed in the key holder?

(A) 360
(B) 720
(C) 1440
(D) 2880
(E) 4320

Source: https://gmath.net
Show more
Our "official solution" is identical to the other two posted above. (Thank you for your contributions!)

Here is our wording:

\(?\,\,\,:\,\,\,\# \,\,{\rm{8 - keys}}\,\,{\rm{placing}}\)

\(?\,\,\, = \,\,\,\underbrace {\,{P_2}\,}_{{\rm{main}}\,\,{\rm{keys}}} \cdot \underbrace {\,{P_6}\,}_{{\rm{other}}\,\,{\rm{keys}}}\,\,\, = \,\,\,2!\,\, \cdot 6! = 2 \cdot 720 = 1440\)


The correct answer is therefore (C).


We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.
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