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[vvaann]

This is the question number 14 from the ETS's "Practicing to take the GRE mathematics test":

A newscast contained the statement that the total use of electricity in city A had declined in one billing period by 5 percent, while household use had declined by 4 percent and all other uses increased by 25 percent. Which of the following must be true about the billing period?

A. The statement was in error.
B. The ratio of all other uses to household use was 29/1.
C. The ratio of all other uses to household use was 29/16.
D. The ratio of all other uses to household use was 29/19.
E. None of the above.

What do you think??

Regards

[matroid]

Dear vvaann,

Please use the

SPOILER: spoiler

tag next time, I love to see the OAs immediately. Anyway, I think the answer should be A (error), because if there were no "other" uses, the overall decline would be 4% only. If "other uses" are positive, then their increase (whatever the rate of growth is) results in a less than 4% decline. So 5% overall decline is impossible.

If you prefer numbers you should be able to transform the problem into a linear(!) equation which yields that household use was 30/29 > 1 part of all use (or sg like this), which is impossible. But I think the previous reasoning is nicer.

Cheers,

Md.

[vvaann]

Thanks for the nice explanation, Matroid.

I was confused by the wording.
Your answer is totally correct according to the OA.

Br,
vvaann