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Bunuel
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John must arrange 3 different physics books and 3 different mathematic 14 Jun 2016, 02:37
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15% (low)

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77% (01:31) correct 23% (01:58) wrong based on 269 sessions

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John must arrange 3 different physics books and 3 different mathematics books on one shelf. If the first book on the leftmost side is a mathematics book and no physics book is next to another physics book. How many different arrangements exist?

A. 6
B. 9
C. 36
D. 120
E. 720
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C
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chetan2u
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John must arrange 3 different physics books and 3 different mathematic 14 Jun 2016, 03:12
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Bunuel
John must arrange 3 different physics books and 3 different mathematics books on one shelf. If the first book on the leftmost side is a mathematics book and no physics book is next to another physics book. How many different arrangements exist?

A. 6
B. 9
C. 36
D. 120
E. 720

First place the maths book -
since all are different books, they can be arranged in 3! ways - 6 ways...

next we have 4 places for physics book, but leftmost is not a valid place as left is always maths..
_M_M_M_, but valid ways are M_M_M_
so 3 places for 3 books - again 3! ways...

Total = \(3!*3! = 36\)

C
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Harish Yannam
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John must arrange 3 different physics books and 3 different mathematic 14 Jun 2016, 03:24
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3! *3 ! = 36
three maths can me arranged 3!ways, 3 physics books in 3! ways
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John must arrange 3 different physics books and 3 different mathematic 14 Jun 2016, 04:42
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First Place, is reserved for Math book. There are 3 Math books which can be arranged in 3 ways

Restriction comes into play :Physics book cannot be together. Hence, the math & the physics books take alternate places

Second Place, Physics Book - in 3 ways
Third Place, Math Book - in 2 ways (only 2 books left)
Fourth Place, Physics - in 2 ways (only 2 Physics book left)
Rest two places can be arranged in one way only.

Total no of ways = 3*3*2*2*1*1 = 36 ways
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John must arrange 3 different physics books and 3 different mathematic 14 Jun 2016, 07:25
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leftmost is reserved for math book so the pattern is M _M_M_
consider maths book first,,they can be placed in 3*2*1 =3! ways
then, physics book can be placed in 3! ways
total ways = 3! *3! = 36
option c
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John must arrange 3 different physics books and 3 different mathematic 15 Feb 2022, 23:28
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Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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