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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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