Math Is Fun Forum
You are not logged in.
- Topics: Active | Unanswered
#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.
Offline
#2 2012-11-15 20:07:22
- Bob
- Administrator
- Registered: 2010-06-20
- Posts: 10,626
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
Sometimes I deliberately make mistakes, just to test you! …………….Bob 
Offline
#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?
Offline
#4 2012-11-17 20:59:11
- Bob
- Administrator
- Registered: 2010-06-20
- Posts: 10,626
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
Sometimes I deliberately make mistakes, just to test you! …………….Bob
Offline
#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.
[removed by administrator]
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: 2,226
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.
May bobbym have a wonderful time in the pearly gates of heaven.
He will be sorely missed.
Offline
#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.
Offline
#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.
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
Offline
#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.
according to bob bundy(thank you)
the Awser is 25
thanks for your help
Offline