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1.6 Exponentials and Logarithms

1.6 Exponentials and Logarithms

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Question 3

The population of a specific bacteria colony (NNN) recorded h h\,h hours after an experiment began is shown in the table below.

hhh12471012
NNN1902906602300790018000

The data is coded using the changes of variable x=hx = hx=h and y=log⁡10Ny = \log_{10} Ny=log10​N.

The regression line of y y\,y on x x\,x is found to be y=2.10+0.18xy = 2.10 + 0.18xy=2.10+0.18x.

a.

Given that the data can be modelled by an equation in the form N=abhN = ab^hN=abh where a a\,a and b b\,b are constants, find the values of a a\,a and b b\,b to 3 significant figures.

[3]
b.

Give an interpretation of the constant a a\,a in this equation.

[1]
c.

Explain why this model might not be reliable for predicting the population after 1 week.

[1]
Markscheme

1.6 Exponentials and Logarithms Questions

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

104 exam-style questions on OCR A Level Maths 1.6 Exponentials and Logarithms, covering 1.6.1 Properties of the exponential function, 1.6.2 Gradient of e^(kx) (A-level only), 1.6.3 Definition of the logarithm, 1.6.4 The natural logarithm function, 1.6.5 ln x as inverse of e^x, 1.6.6 Laws of logarithms, 1.6.7 Equations involving exponentials, 1.6.8 Reduction to linear form, and 1.6.9 Modelling using exponential functions. Each one has a worked solution and a mark scheme showing where the marks go.

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