Name: DiLlOn
Who is asking: Student
Level: Middle
Question:
In the city of Skangai there are 6 million people.Each person has to tell 2 more people that theres going to be an earthquake. After they do they leave the city. There will be no duplications.It takes 3 minutes to tell each person. How long will it take for the whole city to know about the earthquake?
THANX!
Hi Dillon,
I would use a table to keep track of the first few steps.
Time in Minutes  Number told  Population remaining 

0  1  6 000 000 
3  2  5 999 999 
6  4  5 999 997 
9  8  5 999 993 
12  16  5 999 985 
.  .  . 
.  .  . 
.  .  . 
This seems very slow but it soon picks up. I have done 5 rows of the table and you don't need to go far beyond the 20th row.
Can you see a pattern that allows you to solve this problem without constructing the table?
Cheers,
Penny
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