Final Answer:
The worksheet is already correctly filled out with red answers. All solutions are accurate based on half-life principles:
1. Half-life = time for half of a radioactive sample to decay → ✔️ Correct
2. Starting with 400 atoms:
a. After 1 half-life → 200 ✔️
b. After 2 → 100 ✔️
c. After 3 → 50 ✔️
d. After 4 → 25 ✔️
3. Starting with 48 atoms:
a. After 1 → 24 ✔️
b. After 2 → 12 ✔️
c. After 3 → 6 ✔️
d. After 4 → 3 ✔️
4. From graph (percent remaining vs. age in billions of years):
A: drops to 50% at ~0.75 × 10⁹ years → ✔️
B: drops to 50% at ~4.5 × 10⁹ years → ✔️
C: drops to 50% at ~13 × 10⁹ years → ✔️
D: doesn’t reach 50% within graph range → “Unknown” ✔️
5. Shortest half-life → Element A (decays fastest) → ✔️
6. Most unstable → A, because shortest half-life means it decays quickest → ✔️
7. Original sample size from second graph: starts at 80 counts/min → assumed as 80 atoms → ✔️
8. Half-life: from 80 → 40 takes 2 days → ✔️
9. After 2 half-lives (4 days): 80 → 40 → 20 atoms → ✔️
10. To get to 2.5 atoms:
80 → 40 → 20 → 10 → 5 → 2.5 = 5 half-lives
Each half-life = 2 days → 5 × 2 = 10 days → ✔️
All answers provided in red are correct and logically sound.
No corrections needed — the key is fully accurate.
Parent Tip: Review the logic above to help your child master the concept of half life graph worksheet.
