How to use it
Choose the unknown. Enter the other three values using the same amount unit and same time unit. The unknown field is ignored when solving.
Method and worked example
Remaining N = initial N₀ × 2^(−elapsed t ÷ half-life h). Inverse modes rearrange this equation with base-2 logarithms. Amounts and half-life must be positive; elapsed time may be zero.
Example
100 units with a 10-day half-life leave 25 units after 20 days.
Assumptions and limitations
Assumes a constant exponential decay rate. This is a mathematical model, not medical dosing advice, biological treatment guidance, or instructions for radioactive materials.
Privacy and accessibility
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