---
title: "A detector measures the activity of a freshly prepared sample containing an unknown radioisotope as a function of time. The measured activity \\(A\\) in becquerels (\\(\\text{Bq}\\)) over an \\(18\\text{-hour}\\) period is displayed in the graph. Based on the graph, what percentage of the original sample’s radioactive nuclei has decayed after \\(24\\text{ hours}\\)?"
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url: "https://nerd-notes.com/ubq/123526/"
date_modified: "2026-09-28T12:00:02+00:00"
---

# A detector measures the activity of a freshly prepared sample containing an unknown radioisotope as a function of time. The measured activity \(A\) in becquerels (\(\text{Bq}\)) over an \(18\text{-hour}\) period is displayed in the graph. Based on the graph, what percentage of the original sample’s radioactive nuclei has decayed after \(24\text{ hours}\)?

A detector measures the activity of a freshly prepared sample containing an unknown radioisotope as a function of time. The measured activity \(A\) in becquerels (\(\text{Bq}\)) over an \(18\text{-hour}\) period is displayed in the graph. Based on the graph, what percentage of the original sample's radioactive nuclei has decayed after \(24\text{ hours}\)?

![A quantitative plot of Activity A in Bq versus Time t in hours. The horizontal axis ranges from 0 to 18 with vertical grid lines and tick marks every 3 hours labeled 0, 3, 6, 9, 12, 15, and 18. The horizontal axis is labeled t (hours). The vertical axis ranges from 0 to 800 with horizontal grid lines and tick marks every 100 units, with major labels at 0, 200, 400, 600, and 800. The vertical axis is labeled A (Bq). A single smooth, solid curve begins at (0, 800) and decreases exponentially to the right, passing exactly through the grid intersections at (6, 400), (12, 200), and (18, 100). No other labels, lines, curves, or text appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596802-lNt9Gv.jpg)

- **A.** \(6.25\%\)
- **B.** \(75.0\%\)
- **C.** \(87.5\%\)
- **D.** \(93.75\%\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123526/*