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## #1 2012-11-15 19:53:41

cat1kf2
Member
Registered: 2012-11-15
Posts: 3

### 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.

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## #2 2012-11-15 20:07:22

bob bundy
Registered: 2010-06-20
Posts: 8,055

### 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

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #3 2012-11-17 20:54:49

SMBoy
Banned
Registered: 2012-11-17
Posts: 13

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

Is The Answer above correct? as there is no reply?

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## #4 2012-11-17 20:59:11

bob bundy
Registered: 2010-06-20
Posts: 8,055

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

hi SMboy,

Welcome to the forum.

What answer are you talking about ?

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

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #5 2012-11-18 12:37:52

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 2012-11-18 13:46:26

Mathegocart
Member
Registered: 2012-04-29
Posts: 1,878

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

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

The integral of hope is reality.

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## #7 2012-11-18 23:00:55

SMBoy
Banned
Registered: 2012-11-17
Posts: 13

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

Thank's all I understand now how it works.

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## #8 2012-11-21 16:30:00

cat1kf2
Member
Registered: 2012-11-15
Posts: 3

### 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

Thanks for your help Bob

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## #9 2012-11-21 16:38:55

cat1kf2
Member
Registered: 2012-11-15
Posts: 3

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

mathgogocart wrote:

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

thanks for your help

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