Question 76·Easy·Command of Evidence
Energy Efficiency and Lifespan of Four Household Light Bulbs
| Bulb type | Power consumption (watts) | Average lifespan (hours) |
|---|---|---|
| Incandescent | 60 | 1,000 |
| Halogen | 45 | 2,000 |
| Compact fluorescent (CFL) | 14 | 10,000 |
| Light-emitting diode (LED) | 10 | 25,000 |
For a science-fair display, a student must choose a bulb that consumes no more than 15 watts and lasts at least 20,000 hours. Based on the information in the table, she decides to use an ______
Which choice most effectively uses data from the table to complete the text?
For table-based evidence questions, start by underlining the specific numerical conditions in the sentence (limits like “no more than” and “at least”) and translate them into simple comparisons (≤, ≥). Then scan the table to quickly eliminate any options that clearly violate a condition, and only compare details (like lifespan) among the remaining candidates. Always ensure the answer choice satisfies all listed requirements, not just the first one you notice.
Hints
Focus on the conditions in the sentence
Underline the phrases "no more than 15 watts" and "at least 20,000 hours." Think about what each of these means in terms of comparing numbers.
Use the power requirement to narrow the choices
From the table, list which bulbs have power consumption of 15 watts or less. You can immediately eliminate any bulb that uses more than 15 watts.
Then apply the lifespan requirement
Among the bulbs that meet the power requirement, compare their lifespans to 20,000 hours. Which one has an average lifespan that is 20,000 hours or more?
Step-by-step Explanation
Translate the requirements
The prompt says the bulb must:
- consume no more than 15 watts → power consumption must be ≤ 15 watts
- last at least 20,000 hours → lifespan must be ≥ 20,000 hours
Any bulb that fails either condition cannot be chosen.
Check the power consumption first
Look at the "Power consumption" column in the table:
- Incandescent: 60 watts (too high; more than 15)
- Halogen: 45 watts (too high; more than 15)
- CFL: 14 watts (meets the ≤ 15 requirement)
- LED: 10 watts (also meets the ≤ 15 requirement)
So only CFL and LED pass the power requirement. The other two can be eliminated.
Check the lifespan among the remaining bulbs
Now compare the "Average lifespan" of the remaining bulbs (CFL and LED) to the at least 20,000 hours requirement:
- CFL: 10,000 hours → less than 20,000 hours, so it does not meet the lifespan requirement.
- LED: 25,000 hours → greater than 20,000 hours, so it does meet the lifespan requirement.
The only bulb that satisfies both the power and lifespan conditions is the LED bulb, so the correct completion is "LED bulb."