AlgebraHardWhen a linear model reaches zero, from two values
Algebra practice question
A phone's battery is at 90% at 8 a.m. and at 60% at 2 p.m., draining at a constant rate. At what time will it reach 0%?
- A. 2 a.m. the next dayCorrect
- B. 8 p.m.
- C. midnight
- D. 10 p.m.
Answer: A. 2 a.m. the next day
30 percentage points in 6 hours is 5 per hour. From 90% at 8 a.m., reaching 0 takes 18 hours: 2 a.m. the next day.
Why the other answers are wrong
- B. 8 p.m.
- 8 p.m. is 12 hours after 8 a.m., when 30% remains.
- C. midnight
- Midnight is 16 hours on, when 10% remains.
- D. 10 p.m.
- 10 p.m. is 14 hours on, when 20% remains.
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