The world population, PPP (billion), is modelled by P=abtP = ab^tP=abt, where t t\,t is years since 1 April 1974. The linear relationship is log10P=kt+0.6\log_{10}P = kt + 0.6log10P=kt+0.6, where k>0k>0k>0.

Find, to 4 significant figures, the value of a a\,a and find the value of b b\,b in terms of kkk.
With reference to the model interpret (i) the value of the constant aaa, (ii) the value of the constant b b\,b in terms of kkk.
Find the world population, as predicted by the model, on 1 April 2020 in terms of kkk.
Given the world population on April 2020 was 7.8 billion use your answer in part (c) to comment on the suitability of the model in terms of kkk.
277 exam-style questions on Edexcel A Level Maths Exponentials and Logarithms, covering 14.1 Exponential Functions, 14.2 y = e^x, 14.3 Exponential Modelling, 14.4 Logarithms, 14.5 Laws of Logarithms, 14.6 Solving Equations using Logarithms, 14.7 Working with Natural Logarithms, and 14.8 Logarithms and Non-Linear Data. Each one has a worked solution and a mark scheme showing where the marks go.