Science · Grades 10–12
Half-life models
This idealized model halves the expected amount after each equal half-life interval.
The key idea
This idealized model halves the expected amount after each equal half-life interval.
N = N₀(½)ᵏ after k half-lives
Worked examples
An ideal decay model starts with 1792 mg. What expected mass remains after 6 half-lives, in mg?
1792 ÷ 2^6 = 28
28 mg
An ideal decay model starts with 172 mg. What expected mass remains after 2 half-lives, in mg?
172 ÷ 2^2 = 43
43 mg
Try it yourself
An ideal decay model starts with 240 mg. What expected mass remains after 3 half-lives, in mg?
An ideal decay model starts with 208 mg. What expected mass remains after 3 half-lives, in mg?
Check your understanding
Answers and marking notes
- 30 mg
240 ÷ 2^3 = 30
- 26 mg
208 ÷ 2^3 = 26
Further reading and review references
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Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.