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1.6 Exponentials and logarithms

1.6 Exponentials and logarithms

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Question 71

The decay of a radioactive substance is modelled using the formula N=1000e−ktN = 1000e^{-kt}N=1000e−kt where N N\,N is the number of atoms after t t\,t years and k k\,k is a positive constant.

a.

Write down the number of atoms when the substance started to decay.

[1]
b.

Given that it takes 14.4 years for half of the substance to decay, find the value of k k\,k to 3 significant figures.

[4]
c.

Calculate the number of atoms left when t=30t = 30t=30.

[1]
Markscheme

1.6 Exponentials and logarithms Questions

  1. A Level
  2. /Maths
  3. /1.6 Exponentials and logarithms

104 exam-style questions on WJEC A Level Maths 1.6 Exponentials and logarithms, covering 1.6.1 Exponentials and logarithms, 1.6.2 Exponentials and logarithms, 1.6.3 Exponentials and logarithms, 1.6.4 Exponentials and logarithms, 1.6.5 Exponentials and logarithms, 1.6.6 Exponentials and logarithms, 1.6.7 Exponentials and logarithms, 1.6.8 Exponentials and logarithms, and 1.6.9 Exponentials and logarithms. Each one has a worked solution and a mark scheme showing where the marks go.

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