Advanced MathVery hardTime for three halvings
Advanced Math practice question
The mass m, in grams, of a decaying sample after t days is given by m(t) = 80(1/2)^(t/5). After how many days will the mass be 10 grams?
Answer: 15
80 → 40 → 20 → 10 is three halvings, and each takes 5 days: t = 15.
Common wrong answers
- If you answered 3
- 3 is the number of halvings, not the number of days.
- If you answered 5
- 5 days gives one halving, to 40 grams.
- If you answered 8
- 8 is 80 ÷ 10, treating the decay as linear.
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