Question 1188811
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          To solve the problem,  I  prepared this  Table below


<pre>

       T            A            B            L            E


    step                             how many           how mamy 
     #                             teachers know    teachers don't know

     1        a principal               4              60 - 4 = 56
            calls to 4 teachers

     2        4 teachers call
            to 8 other teachers      4 +  8 = 12       56 - 8 = 48 

     3        8 teachers calls
            to 16 other teachers    12 + 16 = 28       48 - 16 = 32 

     4       16 teacher calls
            to 32 other teachers    28 + 32 = 60       32 - 32 =  0 



Now from the table, the number of people (= of teachers) who made 2 calls is  4 + 8 + 16 = 28.


<U>ANSWER</U>.  The number of people who made 2 calls is  28.
</pre>

Solved.



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Now, &nbsp;as you see this solution and this table, &nbsp;you can, &nbsp;probably, organize 

your arguments in other, &nbsp;more compact form to produce your own solution.