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# Data for a research experiment are given in the table above. If the am

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Joined: 02 Sep 2009
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Data for a research experiment are given in the table above. If the am  [#permalink]

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26 Sep 2018, 03:59
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Difficulty:

35% (medium)

Question Stats:

70% (01:15) correct 30% (00:24) wrong based on 30 sessions

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Data for a research experiment are given in the table above. If the amount of microbes present increased by the same fraction during each of the two 4-hour periods shown, how many milligrams of microbes were present at 6:00 pm?

(A) 110
(B) 111
(C) 114
(D) 118
(E) 120

Attachment:

2018-09-26_1557.png [ 22.93 KiB | Viewed 338 times ]

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Re: Data for a research experiment are given in the table above. If the am  [#permalink]

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26 Sep 2018, 07:14
I think the Answer should be B.

The question stem says "increased by the same fraction during each of the two 4-hour periods shown".

This would transalte into $$100+2x=121$$ --> $$2x=21$$ --> $$x=\frac{21}{2}$$ --> $$x=10.5$$

Therefore, after 4 hours --> $$100+10.5=110.5$$ which rounded is $$111$$

If the question stem would say "increased by the same FACTOR during each of the two 4-hour periods shown".
Then the Answer would be A.

Please correct me if I am wrong!
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Re: Data for a research experiment are given in the table above. If the am  [#permalink]

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26 Sep 2018, 22:13
Bunuel Could you explain why it is A? “Increased by a fraction” does that translate into increased by the same amount every time or increased by the same factor??

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Re: Data for a research experiment are given in the table above. If the am  [#permalink]

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29 Sep 2018, 16:56
Bunuel wrote:

Data for a research experiment are given in the table above. If the amount of microbes present increased by the same fraction during each of the two 4-hour periods shown, how many milligrams of microbes were present at 6:00 pm?

(A) 110
(B) 111
(C) 114
(D) 118
(E) 120

Attachment:
2018-09-26_1557.png

At 2pm there were 100 microbes, at 6pm there were 100x microbes, and at 10pm there were 100x^2 microbes, so we have:

100x^2 = 121

x^2 = 121/100

x = 11/10

So at 6pm there were 11/10 * 100 = 110 microbes.

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Re: Data for a research experiment are given in the table above. If the am  [#permalink]

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01 Oct 2018, 10:08
p/100 = 121/p

p^2=121 x 100
p = 11 x 10

Please dont multiply 121 and 100 then worry about calculating the root.

One needs to know that ratios will be same since this is an Geometric Progression. Normally all such questions follow GP or fixed-variance equations
Re: Data for a research experiment are given in the table above. If the am &nbs [#permalink] 01 Oct 2018, 10:08
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