Nine family members: 5 grandchildren (3 brothers and 2 sisters) and their 4 grandparents are to be seated around a circular table. How many different seating arrangements are possible so that 2 sisters are seated between any two of the three brothers?
A. 120
B. 480
C. 1440
D. 2880
E. 8640
Consider two brothers and two sisters between them as one unit: {BSSB}.
So, now we have 6 units: {G}, {G}, {G}, {G}, {B}, and {BSSB}.
These 6 units can be arranged around a circular table in (6-1)!=5! ways.
Next,
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A. 120
B. 480
C. 1440
D. 2880
E. 8640
Consider two brothers and two sisters between them as one unit: {BSSB}.
So, now we have 6 units: {G}, {G}, {G}, {G}, {B}, and {BSSB}.
These 6 units can be arranged around a circular table in (6-1)!=5! ways.
Next,
...