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# M28-20

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Math Expert
Joined: 02 Sep 2009
Posts: 47983

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16 Sep 2014, 01:29
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Difficulty:

45% (medium)

Question Stats:

62% (01:07) correct 38% (01:19) wrong based on 34 sessions

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If the productivity of a brigade grows by 10% when the number of the workers in the brigade is increased by one, then which of the following is closest to the ratio of the productivity of a 12-person brigade to that of a 10-person brigade?

A. 0.21
B. 0.82
C. 1.20
D. 1.21
E. 1.44

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Math Expert
Joined: 02 Sep 2009
Posts: 47983

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16 Sep 2014, 01:29
Official Solution:

If the productivity of a brigade grows by 10% when the number of the workers in the brigade is increased by one, then which of the following is closest to the ratio of the productivity of a 12-person brigade to that of a 10-person brigade?

A. 0.21
B. 0.82
C. 1.20
D. 1.21
E. 1.44

If $$x$$ is the productivity of the 10-person brigade, the productivity of the 12-person brigade is $$1.1*1.1*x = 1.21*x$$. The required ratio $$= \frac{1.21x}{x} = 1.21$$.

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Intern
Joined: 05 Jun 2017
Posts: 7
Location: India
GPA: 3.67
WE: Science (Non-Profit and Government)

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22 Nov 2017, 00:39
1
my method is product change method

let initial value is 100
then 10% increase makes 110. further 10 % increase makes 121

now ratio of 121/100: 1.21
Intern
Joined: 12 Jan 2018
Posts: 19

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14 Jun 2018, 22:22
I have a question here -- I understand how the answer key derives its answer as the 10% compounds with the second additional worker (which is why it is 10 -> 11 -> 12.1 vs 10 = 12.1/10 = 1.21), but can't the productivity have compounded from the second worker, meaning the difference between the 10th and the 12th would be much higher? The question does not seem to imply that the brigade only begins the 10% increase starting with the tenth worker, it just specifies for each additional worker?

Interested to hear thoughts. Thanks!
M28-20 &nbs [#permalink] 14 Jun 2018, 22:22
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# M28-20

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