Probability of sitting at circular table

This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Fri Jun 25, 2010 2:15 pm

Probability of sitting at circular table

by thx5828 » Fri Jun 25, 2010 2:35 pm
I had a question like this on the actual GMAT and not sure of the approach (or answer choices, so I apologize upfront).

The question went something like this:

A, B, C, D, E, and F are to be seated at a circular table. What is the probability that B sits between A and C, C between B and D, D between C and E, E between D and F, and F between A and E?

Also, are questions like this on the actual GMAT common? It seems like a toughie but I could be overthinking it. Thanks!

User avatar
Master | Next Rank: 500 Posts
Posts: 216
Joined: Wed Jul 23, 2008 2:35 am
Location: Pune, India
Thanked: 5 times
GMAT Score:700

by ayushiiitm » Fri Jun 25, 2010 5:38 pm
total nos of arrangements of 6 people on a circular table

is factorial (6-1)= factorial5= 120

nos of favourable arrangements=2
position fixed everybody (option of sitting either clockwise or anticlockwise direction)

hence probability is 2/120=1/60

wats the OA

i dont think its a difficult one
Success is a journey.....enjoy every moment of it

User avatar
Legendary Member
Posts: 1460
Joined: Tue Dec 29, 2009 1:28 am
Thanked: 135 times
Followed by:7 members

by selango » Fri Jun 25, 2010 9:08 pm
Probability of seating arrangements in circle is (n-1)!

Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 am
Thanked: 173 times
Followed by:2 members
GMAT Score:710

by gmatmachoman » Fri Jun 25, 2010 10:54 pm
selango wrote:Probability of seating arrangements in circle is (n-1)!
Nah!! Its the total Number of ways of seating arrangements= (N-1)!

User avatar
Legendary Member
Posts: 1460
Joined: Tue Dec 29, 2009 1:28 am
Thanked: 135 times
Followed by:7 members

by selango » Fri Jun 25, 2010 11:00 pm
Thanks for correcting my mistake