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A certain species of bacteria doubles its population every m minutes.

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A certain species of bacteria doubles its population every m minutes.  [#permalink]

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New post 13 Apr 2018, 02:07
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C
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  55% (hard)

Question Stats:

48% (00:51) correct 52% (01:04) wrong based on 29 sessions

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A certain species of bacteria doubles its population every m minutes. What will be the population of this bacteria colony in 4 hours?

(1) In one hour, the population of the bacteria colony is 20,000.
(2) In three hours, the population of the bacteria colony is 320,000.

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Re: A certain species of bacteria doubles its population every m minutes.  [#permalink]

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New post 13 Apr 2018, 02:19
Bunuel wrote:
A certain species of bacteria doubles its population every m minutes. What will be the population of this bacteria colony in 4 hours?

(1) In one hour, the population of the bacteria colony is 20,000.
(2) In three hours, the population of the bacteria colony is 320,000.


Let the population at start be P. We need to determine P and also m to be able to tell the population after 4 hours.

(1) In one hour ( 60 mins) the population is 20,000.

20,000 = P*(2)^(60/m) Hence Insuff

(2) In three hours ( 180 mins) the population is 320,000.

320,000 = P*(2)^(180/m) Hence Insuff

(1) + (2) combined...

divide eq2 by eq1

16 = 2^(180/m) / 2^(60/m)

2^4 = 2^( 180/m - 60/m)

4 = 180/m - 60/m
4 = 120/m
m = 30 mins

Now we can put the value of m in any of eq1 or eq2 to find the value of P.

With P & m we can find the value of the population @ 4hrs from the start.

Hence Option (C) is our answer.

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Re: A certain species of bacteria doubles its population every m minutes.  [#permalink]

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New post 28 Apr 2018, 06:26
I) insufficient
Gives info only about number in one hour

II) insufficient
Gives info only about number in three hour

Combining gives 120 min it becomes 8 times
Means every 40 min doubling

So C is aNswer

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Re: A certain species of bacteria doubles its population every m minutes. &nbs [#permalink] 28 Apr 2018, 06:26
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