A radioactive substance decays according to , with in years. If its half-life is 10 years, the value of is:

Answer and explanation

Correct answer: D.

  1. Step 1: After 10 years, , so .
  2. Step 2: Take natural logs: , so .
Answer
.
Why not the others: is the inverse of the answer; swaps the roles of 2 and 10; treats half-life as a drop to one fifth.

Practise more Functions, Differential Calculus and Exponential Modelling.

Free questions with an explanation for every one, and full timed NSW HSC mock tests.

A radioactive substance decays according to N = N… | NSW HSC