Data Sufficiency

BTGmoderatorLU wrote:Source: Official Guide

By what % did the median household income in country Y decrease from 1970 to 1980?

(1) In 1970 the median household income in Country Y was 2/3 of the median household income in Country X
(2) In 1980 the median household income in Country Y was 1/2 of the median household income in Country X

The OA is E.

Certainly, each statement alone is insufficient as the first one does not provide any information about 1980, while the second one does not provide any information about 1970.

(1) and (2) together:

[color=]1970:[/color]

Say, the median household income in Country X in 1970 = a; thus,
the median household income in Country Y in 1970 = 2a/3

[color=]1980:[/color]

Say, the median household income in Country X in 1980 = b; thus,
the median household income in Country Y in 1980 = b/2

Thus, the % decrease in the median household income in country Y from 1970 to 1980 = [(2a/3 - b/2) / 2a/3]*100%

Since we do not know the value of a and b, we can't get the answer. Insufficient.

The correct answer: E

Hope this helps!

-Jay
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