2025 Paradigm Sec 3 Mock EOY Q7

2025 Paradigm Sec 3 Mock EOY Q7

Secondary 3
8 marks

[Exponential Word Problem]

The mass, \(m\) grams, of a radioactive substance remaining, \(t\) days after being measured, is given by \(m=10e^{-0.01t}+0.2\).

  1. Find the initial mass.[1]
  2. Sketch the graph \(m=10e^{-0.01t}+0.2\) for \(t\geq0\).[2]
  3. Find the least number of days it takes before the amount of substance is reduced to \(5\%\) of its initial mass.[3]
  4. Explain why the mass of the radioactive substance can never be less than \(0.2\text{ g}\).[2]

Solution:

Solution locked

Sign in to view the step-by-step solution

Similar questions are unavailable for this question.
Answer:(a) \(10.2\text{ g}\); (b) decreasing curve approaching \(m=0.2\); (c) \(348\) days; (d) \(m>0.2\) since the exponential term is positive.

Need help? Join our JC Math tuition classes.

Learn more