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A substance has half of 3 min. After 6 min, the count rate was observed...

Physics
JAMB 2020

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
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Correct Answer: Option A
Explanation

Let the count rate at zero time be N 

N \(\frac{3 min}{\to}\)  \(\frac{N}{2}\) \(\frac{3 min}{\to}\) \(\frac{N}{4}\)

\(\frac{N}{4}\) 

= 400

N = \(\frac{400}{N/4}\) x N 

= 1600

There is an explanation video available below.


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Explanation Video

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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995