Find the activity remaining after a period of decay, work backward to an earlier activity, or calculate the time needed to reach a target. You can also find a half-life from two activities and the time between them.
The calculator uses the handbook relationship λ = 0.693/T½, where 0.693 approximates ln 2. Activity and time inputs have separate unit selectors. The member worked solution shows the sign change for back-decay and the natural logarithm used when solving for time.
Results, input checks, source references and accuracy notes are free. Paid membership adds the step-by-step solution and calculator keystrokesKey sequences for 14 calculator optionsScientific — commonly exam-legalTI-30XaTI-30X IIS / IIBTI-30XS MultiViewTI-34 MultiViewTI-36X ProCasio fx-991EX ClassWizCasio fx-115ES PlusCasio fx-300ES PlusSharp EL-W516TOn screen, no handheld neededRadCon calculator (on screen)Graphing / programmable — practice at homeTI-84 Plus CE (and TI-83/84 family)Casio fx-9750GIII / fx-9860GIIIHP 35sNot sure which you haveGeneric scientificChoose the calculator you use to practice. Check with your testing site which models are allowed in the exam..
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Use this calculator for study and reference. For operational radiological work, follow your site’s controlled procedures and approved references.
Read the handbook for free, then use study sessions and practice tests to check what you’ve learned. Membership includes worked solutions and progress tracking. Access is currently by invitation; sign up to hear when it opens.