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•  » Science: A bacteria doubles its population every 12 hours.

## #1 2012-11-16 18:53:41

cat1kf2
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### Science: A bacteria doubles its population every 12 hours.

After 3 days, there are 1,600 bacteria. How many bacteria were there at the beginning of the first day? Use the work backward strategy.

## #2 2012-11-16 19:07:22

bob bundy
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### Re: Science: A bacteria doubles its population every 12 hours.

hi cat1kf2

Welcome to the forum.

Work backwards:

After 3 days ....................1600

12 hours earlier................   1600 ÷ 2

after two days ..................  ÷ 2 again

12 hours earlier ................  ÷ 2 again

After one day ...................  ÷  2 again

12 hours ealier .................   ÷ 2 again

start ................................  ÷ 2 again

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

SMBoy
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## #4 2012-11-18 19:59:11

bob bundy
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### Re: Science: A bacteria doubles its population every 12 hours.

hi SMboy,

Welcome to the forum.

I gave a method, but deliberately did not say what I thought the answer is.

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

## #5 2012-11-19 11:37:52

Ms_Zee
Guest

### Re: Science: A bacteria doubles its population every 12 hours.

Hi SMboy,
The explanation you received from bob bundy is correct, you just need to work out the result.

Hi;

The use of this site for personal advertising is forbidden. Everyone here is a volunteer. We have teachers, mathematicians, physicists, engineers, students and me all answering questions for nothing. If you would like to add your expertise to our group then that would be fine.

## #6 2012-11-19 12:46:26

mathgogocart
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### Re: Science: A bacteria doubles its population every 12 hours.

according to bob bundy(thank you)
the Awser is 25

woosh! woosh! bye as I go to Kanto.

## #7 2012-11-19 22:00:55

SMBoy
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### Re: Science: A bacteria doubles its population every 12 hours.

Thank's all I understand now how it works.

## #8 2012-11-22 15:30:00

cat1kf2
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### Re: Science: A bacteria doubles its population every 12 hours.

#### bob bundy wrote:

hi cat1kf2

Welcome to the forum.

Work backwards:

After 3 days ....................1600

12 hours earlier................   1600 ÷ 2

after two days ..................  ÷ 2 again

12 hours earlier ................  ÷ 2 again

After one day ...................  ÷  2 again

12 hours ealier .................   ÷ 2 again

start ................................  ÷ 2 again

Bob

## #9 2012-11-22 15:38:55

cat1kf2
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### Re: Science: A bacteria doubles its population every 12 hours.

#### mathgogocart wrote:

according to bob bundy(thank you)
the Awser is 25