Grade 11 · Science
Select a backup design for a specified load
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System A: supplies 110 W; tested duration 4 h; cost 10 units. System B: supplies 105 W; tested duration 2 h; cost 6 units. System C: supplies 95 W; tested duration 5 h; cost 5 units.
A model backup system must supply at least 100 W for at least 3 h under the stated test. Which eligible system has the lowest listed cost?
- System C
- System B
- Choose by power alone.
- System A
See the answer & why
System A
Both power and duration must pass. System A has the lowest listed cost among the qualifying systems; the conclusion applies to these stated trials.
A little hint: Check power and duration together before comparing cost.
State the required load and operating duration separately; high power alone does not establish enough operating time.
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