The Communicative Sisters
Six sisters keep in touch with each other by phone every Sunday evening. When two sisters make contact, they update each other on the news about themselves and about any news gleaned about their other sisters from previous calls that day.
What is the smallest number of phone calls required for all the six sisters to be updated about each other?
The answer is 8.
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1 solution
Mark each sister: 1 2 3 4 5 6.
They communicate in this order:
1) 2 - 3
2) 3 - 1
3) 5 - 6
4) 6 - 4
5) 1 - 4
6) 3 - 6
7) 2 - 3
8) 4 - 5