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Nihit
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 08 Sep 2008, 05:47
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AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 10.0 grams
4:00 P.M. x grams
7:00 P.M. 14.4 grams

Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.?

A. 12.0
B. 12.1
C. 12.2
D. 12.3
E. 12.4

guys can anyone provide a short approach to this one without using quadratic equations or plugging answers ?
thanks in advance



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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 08 Sep 2008, 07:12
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Let the amount of increase from 1-4pm and 4-7pm be y.

The equations can be written as
10+y=x - (1)
x+y=14.4 - (2)

Solving the 2 equations we get x=12.2

Answer C.
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 08 Sep 2008, 08:32
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Nihit
AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 10.0 grams
4:00 P.M. x grams
7:00 P.M. 14.4 grams

Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.?

A. 12.0
B. 12.1
C. 12.2
D. 12.3
E. 12.4

guys can anyone provide a short approach to this one without using quadratic equations or plugging answers ? thanks in advance
Show more

x/10 = 14.4/x
x = 12

A.
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 08 Sep 2008, 08:46
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Nihit
AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 10.0 grams
4:00 P.M. x grams
7:00 P.M. 14.4 grams

Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.?

A. 12.0
B. 12.1
C. 12.2
D. 12.3
E. 12.4

guys can anyone provide a short approach to this one without using quadratic equations or plugging answers ?
thanks in advance
Show more

(x-10)/10 =(14.4-x)/x
x*x=144
x=12
A
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 08 Sep 2008, 08:50
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Nihit
AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 10.0 grams
4:00 P.M. x grams
7:00 P.M. 14.4 grams

Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.?

A. 12.0
B. 12.1
C. 12.2
D. 12.3
E. 12.4

guys can anyone provide a short approach to this one without using quadratic equations or plugging answers ?
thanks in advance
Show more

My approach is the same as that above me.

(Time,Amount)
(0,10)
(3, 10x)
(6,10x^2)

Since
10(x^2) = 14.4
100(x^2) = 144 ---------- x 10
x^2 = 144/100
|x| = 12/10 ---------- sqrt
x = +1.2, -1.2

x can only be positive. Therefore, the amount of bacteria at 4:00PM = 10*1.2 = 12

A
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 09 Sep 2008, 11:14
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What is the OA?

Does "increase by same fraction" mean the ratio? To me, this means the difference and not the fraction and with this logic, x - 10 = 14.4 - x => x = 12.2

Am I interpreting something wrong here?
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AMOUNT OF BACTERIA PRESENT Time Amount 1:00 P.M. 10.0 grams 09 Sep 2008, 11:21
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Nihit
AMOUNT OF BACTERIA PRESENT
Time Amount
1:00 P.M. 10.0 grams
4:00 P.M. x grams
7:00 P.M. 14.4 grams

Data for a certain biology experiment are given in the table above. If the amount of bacteria present increased by the same fraction during each of the two 3-hour periods shown, how many grams of bacteria were present at 4:00 P.M.?

A. 12.0
B. 12.1
C. 12.2
D. 12.3
E. 12.4

guys can anyone provide a short approach to this one without using quadratic equations or plugging answers ?
thanks in advance
Show more

The best way to solve this should be thru options.

Taking first option: 12

So from 10 to 12.. the percentage increase is 20 percent.

Similarly, from 12 to 14.4 the percentage increase is 20 percent.

SInce its the same percentage increase in both the cases, A has to be the answer.



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Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!