A substance has half of 3 min. After 6 min, the count rate was observed to be 400. What was its count rate at zero time?

A. 1600
B. 1200
C. 200
D. 2400

Correct Answer: Option A

Explanation

Let the count rate at zero time be N

Let the count rate at zero time be N

N → 3min; → 3min → ^N/₂; ^N/₄ → 3min

= 400 →

800 →1600

= 1600