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A certain species of bacteria doubles its population every m minutes. 13 Apr 2018, 02:07
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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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C
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A certain species of bacteria doubles its population every m minutes. 13 Apr 2018, 02:19
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Bunuel
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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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.

Best,
Gladi
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A certain species of bacteria doubles its population every m minutes. 28 Apr 2018, 06:26
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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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A certain species of bacteria doubles its population every m minutes. 16 Aug 2019, 09:10
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Hi Can you please explain the formula that you have used? Why is it 60/m?
Gladiator59
Bunuel
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.

Best,
Gladi
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A certain species of bacteria doubles its population every m minutes. 10 Jan 2021, 22:00
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Gladiator59
Bunuel
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.

Best,
Gladi
Show more


Whats the use of m here?

the nth term of GP is a(r^n-1) that is what used here? am i correct?

than 20000= P(2^59-1) ; This equation should come.

please correct me.
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A certain species of bacteria doubles its population every m minutes. 23 Sep 2024, 06:27
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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.

I'm confused, because the problem doesn't tell you WHEN exactly the population doubles, only what's the population after 1 hr or 3 hrs. E.g. if population doubles every 33mins, you'd still have have 20k in 60mins, and 320k in 180mins, but population will be different in 240mins from what it'd be if it doubled every 30mins. There could be one more or less doubling.

Answer E, imho.
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A certain species of bacteria doubles its population every m minutes. 28 Sep 2025, 08:35
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