Grade 11 · Science
Select a backup design for a specified load
Evaluate a model backup system against power, duration and cost requirements.
6 authored questions + worked example
Worked example
System A: supplies 70 W; tested duration 4 h; cost 8 units.
System B: supplies 65 W; tested duration 2 h; cost 5 units.
System C: supplies 50 W; tested duration 5 h; cost 4 units.
A model backup system must supply at least 60 W for at least 3 h under the stated test. Which eligible system has the lowest listed cost?
Answer & why
Answer: 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.
All questions
All 6 authored questions for this skill.
Question 1
System A: supplies 55 W; tested duration 3 h; cost 7 units.
System B: supplies 60 W; tested duration 4 h; cost 6 units.
System C: supplies 45 W; tested duration 5 h; cost 3 units.
A model backup system must supply at least 50 W for at least 2 h under the stated test. Which eligible system has the lowest listed cost?
- System B
- System A
- Choose by power alone.
- System C
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: System B
Both power and duration must pass. System B has the lowest listed cost among the qualifying systems; the conclusion applies to these stated trials.
Question 2
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
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: 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.
Question 3
System A: supplies 75 W; tested duration 6 h; cost 12 units.
System B: supplies 80 W; tested duration 4 h; cost 7 units.
System C: supplies 72 W; tested duration 5 h; cost 10 units.
A model backup system must supply at least 70 W for at least 5 h under the stated test. Which eligible system has the lowest listed cost?
- System C
- System B
- System A
- Choose by power alone.
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: System C
Both power and duration must pass. System C has the lowest listed cost among the qualifying systems; the conclusion applies to these stated trials.
Question 4
System A: supplies 95 W; tested duration 3 h; cost 8 units.
System B: supplies 100 W; tested duration 4 h; cost 11 units.
System C: supplies 85 W; tested duration 5 h; cost 4 units.
A model backup system must supply at least 90 W for at least 2 h under the stated test. Which eligible system has the lowest listed cost?
- System C
- System B
- System A
- Choose by power alone.
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: 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.
Question 5
System A: supplies 70 W; tested duration 4 h; cost 8 units.
System B: supplies 65 W; tested duration 2 h; cost 5 units.
System C: supplies 50 W; tested duration 5 h; cost 4 units.
A model backup system must supply at least 60 W for at least 3 h under the stated test. Which eligible system has the lowest listed cost?
- System C
- Choose by power alone.
- System A
- System B
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: 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.
Question 6
System A: supplies 90 W; tested duration 3 h; cost 6 units.
System B: supplies 85 W; tested duration 5 h; cost 9 units.
System C: supplies 75 W; tested duration 6 h; cost 5 units.
A model backup system must supply at least 80 W for at least 4 h under the stated test. Which eligible system has the lowest listed cost?
- System C
- System A
- Choose by power alone.
- System B
A hint
Check power and duration together before comparing cost.
Answer & why
Answer: System B
Both power and duration must pass. System B has the lowest listed cost among the qualifying systems; the conclusion applies to these stated trials.
