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Bunuel
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The Population of a city, which was x in January, increases by a certa 29 Sep 2015, 05:04
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A
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55% (hard)

Question Stats:

62% (01:47) correct 38% (02:20) wrong based on 181 sessions

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The Population of a city, which was x in January, increases by a certain amount in February of the same year and becomes y. Then y increases by a certain amount in March of the same year and becomes z. Is the percentage change from x to y greater than that from y to z?

(1) y – x = z - y

(2) x =150, z = 300

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A
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The Population of a city, which was x in January, increases by a certa 29 Sep 2015, 06:26
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Bunuel
The Population of a city, which was x in January, increases by a certain amount in February of the same year and becomes y. Then y increases by a certain amount in March of the same year and becomes z. Is the percentage change from x to y greater than that from y to z?

(1) y – x = z - y

(2) x =150, z = 300

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Requirement: (z/y-1) - (y/x-1)

(1) y – x = z - y
Do not know x, y => INSUF
(2) x =150, z = 300
Do not know: y => INSUF

(1)+(2) => The value of X, Y, and Z => (z/y-1) - (y/x-1)

SUFFICIENT

Ans: C
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The Population of a city, which was x in January, increases by a certa 29 Sep 2015, 13:03
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Answer = A
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Jonas84
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The Population of a city, which was x in January, increases by a certa 30 Sep 2015, 11:29
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I believe the answer is A. Please see below for explanation.

0) The Population of a city, which was x in January, increases by a certain amount in February of the same year and becomes y. Then y increases by a certain amount in March of the same year and becomes z. Is the percentage change from x to y greater than that from y to z?

from the question stem we get is (y-x) / x > (z - y) / y

Percentage change = (New Value - Old Value) / Old Value

(1) y – x = z - y

From statement 1 if we plug a random number into the inequality we get from the question stem we get 5/x > 5/y this means that the percentage change of x to y is greater than the percentage change of y to z. Sufficient

(2) x =150, z = 300

Statement 2 doesn't tell us anything about y so insufficient.


Answer A
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The Population of a city, which was x in January, increases by a certa 27 Jan 2025, 04:36
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i) y – x = z - y Given

It means the change in population is constant, but since x < y < z so percent change of y-x is > than z-y
Sufficient

ii) x =150, z = 300
Doesn't give any info on y
Insufficient
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