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Expression of IdeasHardSynthesis: lamps over fifteen thousand hours

Expression of Ideas practice question

While researching a topic, a student has taken the following notes: - An LED lamp costs 8 dollars, uses 10 watts, and lasts 15,000 hours. - A halogen lamp costs 2 dollars, uses 50 watts, and lasts 2,000 hours. - Electricity costs 20 cents per kilowatt-hour.

The student wants to argue that the LED lamp is cheaper over 15,000 hours of use. Which choice most effectively uses relevant information from the notes to accomplish this goal?

  1. A. Over 15,000 hours the LED costs 8 dollars for the lamp plus 30 dollars in electricity, 38 in all, while halogen would need eight lamps and 150 dollars in electricity, 166 in all.Correct
  2. B. The halogen lamp costs only 2 dollars.
  3. C. The LED lamp uses 10 watts.
  4. D. Electricity costs 20 cents per kilowatt-hour.

Answer: A. Over 15,000 hours the LED costs 8 dollars for the lamp plus 30 dollars in electricity, 38 in all, while halogen would need eight lamps and 150 dollars in electricity, 166 in all.

Totals for both.

Why the other answers are wrong

B. The halogen lamp costs only 2 dollars.
Favours halogen.
C. The LED lamp uses 10 watts.
One figure, no total.
D. Electricity costs 20 cents per kilowatt-hour.
One figure, no total.

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