Difference between revisions of "1971 Canadian MO Problems/Problem 10"

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== Problem ==
 
== Problem ==
Two flag poles of height <math>h</math> and <math>k</math> are situated <math>2a</math> units apart on a level surface. Find the set of all points on the surface which are so situated that the angles of elevation of the tops of the poles are equal.  
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Suppose that <math>n</math> people each know exactly one piece of information, and all <math>n</math> pieces are different. Every time person <math>A</math> phones person <math>B</math>, <math>A</math> tells <math>B</math> everything that <math>A</math> knows, while <math>B</math> tells <math>A</math> nothing. What is the minimum number of phone calls between pairs of people needed for everyone to know everything? Prove your answer is a minimum.  
  
 
== Solution ==
 
== Solution ==
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== See Also ==
 
== See Also ==
{{Old CanadaMO box|num-b=9|num-a=Last Question|year=1971}}
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{{Old CanadaMO box|num-b=9|after=Last Question|year=1971}}
  
 
[[Category:Intermediate Combinatorics Problems]]
 
[[Category:Intermediate Combinatorics Problems]]

Revision as of 15:55, 12 September 2012

Problem

Suppose that $n$ people each know exactly one piece of information, and all $n$ pieces are different. Every time person $A$ phones person $B$, $A$ tells $B$ everything that $A$ knows, while $B$ tells $A$ nothing. What is the minimum number of phone calls between pairs of people needed for everyone to know everything? Prove your answer is a minimum.

Solution

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See Also

1971 Canadian MO (Problems)
Preceded by
Problem 9
1 2 3 4 5 6 7 8 Followed by
Last Question