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505-555 (Easy)|   Exponents|      
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Bunuel
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A population of a colony of bacteria increases by 20 percent every 3 05 Jun 2018, 02:23
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84% (01:43) correct 16% (02:05) wrong based on 147 sessions

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A population of a colony of bacteria increases by 20 percent every 3 minutes. If at 9:00am the colony had a population of 144,000, what was the population of the colony at 8:54am?

(A) 100,000
(B) 112,000
(C) 120,000
(D) 121,000
(E) 136,000
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A
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A population of a colony of bacteria increases by 20 percent every 3 05 Jun 2018, 03:10
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Bunuel
A population of a colony of bacteria increases by 20 percent every 3 minutes. If at 9:00am the colony had a population of 144,000, what was the population of the colony at 8:54am?

(A) 100,000
(B) 112,000
(C) 120,000
(D) 121,000
(E) 136,000
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From 8:54 to 9:00 we have two 3-minute cycles.

\(x*1.2*1.2=144000\)
\(x=100000\)

Answer: A
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A population of a colony of bacteria increases by 20 percent every 3 05 Jun 2018, 05:28
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Solution



Given:
    • A population of a colony of bacteria increases by 20% in every 3 minutes
    • At 9:00 am the population was 144,000

To find:
    • The population of the colony of bacteria at 8:54 am

Approach and Working:
If we assume the population at 8:54 am to be x, then
    • The population at 8:57 am = 1.2x
    • The population at 9:00 am = 1.2 * 1.2x = 1.44x

Given that,
    • 1.44x = 144000
    Or, x = \(\frac{144000}{1.44}\) = 100000

Hence, the correct answer is option A.

Answer: A
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A population of a colony of bacteria increases by 20 percent every 3 05 Jun 2018, 05:40
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Bunuel
A population of a colony of bacteria increases by 20 percent every 3 minutes. If at 9:00am the colony had a population of 144,000, what was the population of the colony at 8:54am?

(A) 100,000
(B) 112,000
(C) 120,000
(D) 121,000
(E) 136,000
Show more

At first pay kind attention to time. It's given that time interval is between 9.00 and 8.54. 6mins in total. In every 3 mins bacteria population increases by 20%.
we can plot the data as follow:

8.54...................8.57...........................9.00
x........................1.2x...........................1.2*1.2*x

As per the question:
1.2*1.2*x=144000
1.44x=144000
(144/100)x=144000
x=(144000*100)/144
x=100000
Thus at 8.54 a.m. total number of bacteria was 100000.

So, the correct answer is A.
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A population of a colony of bacteria increases by 20 percent every 3 06 Jun 2018, 16:38
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Bunuel
A population of a colony of bacteria increases by 20 percent every 3 minutes. If at 9:00am the colony had a population of 144,000, what was the population of the colony at 8:54am?

(A) 100,000
(B) 112,000
(C) 120,000
(D) 121,000
(E) 136,000
Show more

We can let the population of the colony of bacteria at 8:54 = x. Thus, at 8:57 it was 1.2x, and at 9am, it was 1.2(1.2)x = 1.44x. So we have:

1.44x = 144,000

x = 100,000

Answer: A
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A population of a colony of bacteria increases by 20 percent every 3 12 Jul 2019, 11:26
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Let the value at 8:45 be x

now for every 3 minutes the values increases by 20% and we have total six minutes.

For first 3 minutes -> x + x(20%) = 1.2x

Now next 3 minutes = 1.2x + 20%(1.2x)

Now this values 1.2x + 20%(1.2x) = 144000

=> 12/10(x) + 24/100 (x) = 144000
=> 120x + 24x / 100 = 144000
=> 144x / 100 = 144000
=> x = 100000

Option A.
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A population of a colony of bacteria increases by 20 percent every 3 01 Jun 2023, 07:12
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