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During a certain month, 20 percent of all the electricity used by a ho

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Afroditee
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During a certain month, 20 percent of all the electricity used by a ho [#permalink] New post   16 Dec 2022, 11:55
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During a certain month, 20 percent of all the electricity used by a household was used by the water heater. The cost per kilowatt-hour of the electricity used by the water heater was half the cost per kilowatt-hour of the rest of the electricity used. For that month, the cost of the electricity used by the water heater was what fraction of the cost of the electricity used by the household?

A. \(\frac{1}{11}\)

B. \(\frac{1}{9}\)

C. \(\frac{1}{8}\)

D. \(\frac{1}{5}\)

E. \(\frac{1}{4}\)
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Afroditee
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Re: During a certain month, 20 percent of all the electricity used by a ho [#permalink] New post   17 Dec 2022, 07:33
Is there any faster way to solve this one?

Thanks..
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During a certain month, 20 percent of all the electricity used by a ho [#permalink] New post   17 Dec 2022, 07:48
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Afroditee wrote:
During a certain month, 20 percent of all the electricity used by a household was used by the water heater. The cost per kilowatt-hour of the electricity used by the water heater was half the cost per kilowatt-hour of the rest of the electricity used. For that month, the cost of the electricity used by the water heater was what fraction of the cost of the electricity used by the household?

A. \(\frac{1}{11}\)

B. \(\frac{1}{9}\)

C. \(\frac{1}{8}\)

D. \(\frac{1}{5}\)

E. \(\frac{1}{4}\)


Say the household used 100 units of the electricity that month.

20 units is used by the water heater.
80 units is used by the the rest of the household.

20 units used by the water heater * $0.5 per unit = $10.
80 units used by the the rest of the household * $1 per unit = $80.

(the cost of the electricity used by the water heater)/(total) = 10/(10 + 80) = 1/9.

Answer: B.
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Re: During a certain month, 20 percent of all the electricity used by a ho [#permalink] New post   17 Dec 2022, 09:37
Bunuel wrote:
Afroditee wrote:
During a certain month, 20 percent of all the electricity used by a household was used by the water heater. The cost per kilowatt-hour of the electricity used by the water heater was half the cost per kilowatt-hour of the rest of the electricity used. For that month, the cost of the electricity used by the water heater was what fraction of the cost of the electricity used by the household?

A. \(\frac{1}{11}\)

B. \(\frac{1}{9}\)

C. \(\frac{1}{8}\)

D. \(\frac{1}{5}\)

E. \(\frac{1}{4}\)


Say the household used 100 units of the electricity that month.

20 units is used by the water heater.
80 units is used by the the rest of the household.

20 units used by the water heater * $0.5 per units = $10.
80 units used by the the rest of the household * $1 per units = $80.

(the cost of the electricity used by the water heater)/(total) = 10/(10 + 80) = 1/9.

Answer: B.


Thank you Bunuel, you are the life saver.
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Re: During a certain month, 20 percent of all the electricity used by a ho [#permalink] New post   26 Feb 2024, 20:01
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: During a certain month, 20 percent of all the electricity used by a ho [#permalink]
26 Feb 2024, 20:01
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