Question 1188811: a school with 60 teachers is on alert during a nighttime
storm
to inform teachers whether the school will open the next day , the princeipal will call four teachers
each of whom will then call 2 others
and each of these will again call 2 others
so on untill all 60 have been contacted
how many people have to make 2 calls?
Answer by ikleyn(52873)   (Show Source):
You can put this solution on YOUR website! .
To solve the problem, I prepared this Table below
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.
ANSWER. The number of people who made 2 calls is 28.
Solved.
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Now, as you see this solution and this table, you can, probably, organize
your arguments in other, more compact form to produce your own solution.
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