Advanced MathHardTime for a drug to fall to a level
Advanced Math practice question
A patient has 400 milligrams of a drug in the bloodstream, and the amount halves every 3 hours. After how many hours will 50 milligrams remain?
Answer: 9
400 → 200 → 100 → 50 is three halvings, and each takes 3 hours: 3 × 3 = 9 hours.
Common wrong answers
- If you answered 3
- 3 hours is one halving, leaving 200 mg.
- If you answered 8
- 8 is 400/50, the factor of reduction, not the number of hours.
- If you answered 24
- 24 is 8 × 3, treating the factor 8 as the number of halvings; 8 = 2³, so there are 3 halvings.
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