AlgebraHardWhen two batteries show the same charge
Algebra practice question
Phone A's battery is at 80% and loses 10 percentage points per hour. Phone B's battery is at 50% and loses 4 percentage points per hour. After how many hours will the two batteries show the same charge?
Answer: 5
80 − 10t = 50 − 4t gives 30 = 6t, so t = 5.
Common wrong answers
- If you answered 3
- 3 divides 30 by 10, ignoring phone B's drain.
- If you answered 30
- 30 is the difference in starting charge, not the time.
- If you answered 2.14
- 2.14 divides 30 by 14, adding the rates instead of subtracting.
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