Brain Teasers
Crime Calls
There has been a murder on a street of bungalows. There are 10 bungalows. Each person who lives in a bungalow knows one unique piece of information. To solve the crime everybody needs to know everything. They decide to share their information by phone.
What is the minimum number of calls that need to be made to solve the crime?
What is the minimum number of calls that need to be made to solve the crime?
Answer
16Name the 10 people with letters: A, B, C, ... and so on. A through F each call any one of G, H, I, or J (it doesn't matter which one). That makes six calls so far. Then G calls H and I calls J, after which G calls I and H calls J. Now we've used 10 calls, and G, H, I, and J all know everything. Finally, each of A through F is called by someone in G through J - 6 more calls to get everyone knowing everything. 16 calls in all.
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